MEMCAL    .SCHOOL 
LIEIBAIEY 


d allege  erf 


LABORATORY  EXERCISES 


IN 


BOTANY 


DESIGNED  FOR  THE  USE  OF 


COLLEGES  AND  OTHEK  SCHOOLS  IN  WHICH  BOTANY 
IS  TAUGHT  BY  LABOKATOKY  METHODS 


BY 

EDSON  S.^BASTIN,  A.M. 

PROFESSOR  OF  MATERIA  MEDICA  AND  BOTANY  AND  DIRECTOR  OF  THE  MICROSCOPICAL 
LABORATORY  IN  THE  PHILADELPHIA  COLLEGE  OF  PHARMACY. 


ILLUSTRATED  WITH   7  FIGURES  IN  THE  TEXT, 

AND   87   FULL-PAGE  PLATES   FROM  ORIGINAL   DRAWINGS, 

COMPRISING  UPWARD   OF  250  FIGURES. 


PHILADELPHIA 

W.    B.    SAUNDERS 

925  WALNUT  STREET. 
1895. 


COPYRIGHT,  1894,  BY 
W.   B.    SAUNDERS. 


ELECTROTYPED    BY 
KESTCOTT  ft  THOMSON,   PHILADA. 


PRESS   OF 
W.   B.   SAUNDERS.   PHILADA. 


PREFACE. 


THIS  book  has  had  its  birth  in  the  laboratory.  It  embodies 
methods  that  have  been  evolved  during  many  years  of  observa- 
tion and  experience  in  conducting  a  botanical  laboratory  for  stu- 
dents of  pharmacy.  It  aims  to  inculcate  in  the  student,  by  the 
study  of  properly-selected  examples,  a  knowledge  of  the  ele- 
mentary principles  of  botany,  to  develop  his  observing  faculties, 
to  stimulate  in  him  the  spirit  of  investigation,  and  to  lead  him  to 
take  delight  in  a  beautiful  science. 

While  the  course  here  laid  down  is  strictly  an  elementary  one, 
and  aims  to  cover  only  a  small  part  of  a  wide  and  interesting 
field,  an  effort  has  been  made  in  the  selection  and  arrangement  of 
themes  to  lay  a  sound  foundation  for  the  pursuit  of  the  more  dif- 
ficult branches  of  the  science.  The  intelligent  student  who  has 
completed  the  course  in  a  thorough  manner  may  not  yet  be  a 
botanist,  but  he  will  have  acquired  both  the  methods  and  the 
spirit  that  fit  him  for  original  work  in  the  science. 

Two  things  have  been  kept  steadily  in  view  in  the  preparation 
of  the  book :  the  needs  of  private  students  pursuing  botany  with- 
out the  aid  of  a  teacher,  and  the  requirements  of  such  schools  and 
colleges  as  have  cast  aside  the  old  text-book  methods  of  worrying 
the  students  with  botanical  hard  names,  and  have  adopted  natural 
methods  of  teaching  botany.  It  is  believed  that  the  illustrations 
of  plant-structure  that  accompany  each  exercise — all  of  which 
were  drawn  by  the  author  from  natural  objects,  and  were  repro- 
duced for  the  book  by  photographic  process — will  greatly  smooth 


4  PREFACE. 

the  way  for  the  private  student,  and  also  be  of  considerable  ser- 
vice both  to  teachers  and  classes  in  the  college  laboratory. 

The  book  is  written  in  two  parts,  the  first  dealing  chiefly  with 
the  gross  structure  of  flowering  plants,  or  that  which  may  be  ob- 
served with  no  further  aid  than  that  of  a  simple  microscope,  and 
the  second  devoted  chiefly  to  the  microscopic  structure  of  plants. 
The  plan  pursued  is  similar  in  all  the  exercises.  Each  is  a  study, 
made  direct  from  Nature,  of  some  plant,  plant-organ,  tissue,  or 
product,  and  the  student  is  expected  first  of  all  to  verify  the  de- 
scriptions and  drawings  by  observations  of  his  own,  and  then  to 
make  independently  one  or  more-  parallel  studies  of  some  similar 
object  or  objects  selected  from  the  list  given  in  the  exercise. 

It  has  not  been  deemed  wise  to  cumber  the  book  with  numerous 
descriptions  of  processes  and  methods,  but  there  have  been  given 
only  the  most  useful  and  those  whose  value  has  been  well  proved 
by  experience.  While,  also,  the  list  of  apparatus,  reagents,  stains, 
and  mounting  media  might  have  been  lengthened  very  materially, 
it  is  thought  to  include  all  the  essentials  for  an  elementary  course, 
and  to  be  therefore  of  more  practical  value,  and  less  confusing  to 
beginners,  than  a  more  extended  list. 

For  many  of  the  formulae  for  the  preparation  of  reagents  and 
stains,  and  for  some  processes,  the  author  acknowledges  his  in- 
debtedness to  the  admirable  books  of  E.  Strasburger,  A.  Ziin- 
mermann,  and  Arthur  Bolles  Lee. 

EDSON  S.  BASTIN. 

PHILADELPHIA,  Sept.  15,  1894. 


CONTENTS. 


PAGE 

GENEEAL  INTRODUCTION .15 


PART  L— ORGANOGRAPHY. 

INTRODUCTION ....  17 

EXERCISE  1 23 

STUDY  OF  ROOTS:  I.  External  Characteristics,  23:  (1)  Parts,  23;  (2)  Shape, 
24;  (3)  Kind,  24;  (4)  Branches  and  other  Appendages,  24;  (5)  Mark- 
ings, 24 ;  (6)  Color,  25  ;  (7)  Measurements,  25  ;  (8)  Drawing,  25.  II.  In- 
ternal Structure,  25:  (1)  Transverse  Section  of  Root,  25;  (2)  Longitudi- 
nal Section,  26;  (3)  Tests,  26:  (a)  Iodine,  26;  (6)  Phloroglucin,  27; 
(c)  Ferric-chloride,  27.  (4)  Drawing,  28 ;  (5)  Transverse  Section  of 
Crown,  28. 

EXERCISE  II 31 

STUDY  OF  STEMS  :  I.  External  Characteristics,  31 ;  Parts  and  Markings, 
31.  II.  Structure  of  Terminal  Bud,  32.  III.  Internal  Structure  of  Stem,  33. 

EXERCISE  III 39 

STUDY  OF  STEMS:  COMPARISON  OF  TWIGS:  (1)  External  Characteristics, 
39 :  (1)  Phyllotaxy,  39 ;  (2)  Leaf-scars,  41 ;  (3)  Bud- scales,  42. 

EXERCISE  IV 45 

STUDY  OF  STEMS  :  THE  RHIZOME  :  A. — I.  External  Characteristics,  45. 
II.  Structure  of  Terminal  Bud,  46.  '  III.  Internal  Structure  of  Rhizome,  48. 
B. — I.  External  Appearance  and  Characteristics,  49.  II.  Internal  Structure 
of  Terminal  Bud,  50.  III.  Internal  Structure  of  Rhizome,  50. 

EXERCISE  V 57 

STUDY  OF  STEMS:  THE  TUBER:  1.  External  Characteristics,  57:  (1)  Axil- 
lary Buds,  57  ;  (2)  Leaf-scars,  58 ;  (3)  Terminal  Bud,  58 ;  (4)  Phyllotaxy, 
59.  II.  Internal  Structure,  59:  (1)  Arrangement  of  Tissues,  59;  (2) 
Tests,  60. 

EXERCISE  VI 65 

STUDY  OF  STEMS:  THE  CORM:  I.  External  Characteristics,  65:  (1)  Scales 
and  Buds,  65;  (2)  The  Stem,  65;  (3)  Tests,  66. 

5 


b  CONTENTS. 

PAGE 

EXERCISE  VII 69 

STUDY  OF  STEMS:  THE  BULB:  I.  Scaly  Bulb  of  Lilium  Candidum,  69; 
(1)  Difference  from  a  Corm,  69;  (2)  Nature  of  Scales,  69;  (3)  Likeness 
of  Bulb  to  Bud,  70;  (4)  Roots,  70;  (5)  Venation  of  Scales,  70;  (6)  Cross- 
section  of  Stem,  70.  II.  Tunicated  Bulb  of  Amaryllis  Formositssima,  70 : 

(1)  Definition,  71;  (2)  Scales,  71. 

EXERCISE  VIII 75 

STUDY  OF  A  LEAF:  (1)  The  Parts,  76;  (2)  The  Lamina,  76;  (3)  The  Two 
Surfaces,  77 ;  (4)  Shape  of  Lamina,  78 ;  (5)  Surface  of  Lamina,  78 ;  (6) 
Texture  of  Lamina,  78;  (7)  The  Petiole,  79;  (8)  The  Stipules,  79. 

EXERCISE  IX , 83 

STUDY  OF  PREFOLIATION  :  (1)  Prefoliation  of  Beech,  83;  (2)  Prefoliation 
of  Clover,  84 ;  (3)  Prefoliation  of  Yellow  Dock,  84. 

EXERCISE  X 89 

TYPES  OF  LEAF-VENATION:  (1)  Moss  Leaf,  89;  (2)  Forked  or  Furcate 
Venation,  90;  (3)  Nerved  or  Parallel  Venation,  91;  (4)  Reticulate  or 
Netted  mode  of  Venation,  92 :  (a)  Pinni-reticulate  Leaf,  (6)  Palmi-retic- 
ulate  Leaf,  (c)  Costate-reticulate  or  Rib-netted  Leaf,  93. 

EXERCISE  XI 101 

THE  BRANCHING  OF  LEAVES  :  (1 )  Leaf  of  Dandelion,  102 ;  (2)  Leaf  of 
Trumpet  Creeper,  102;  (3)  Leaf  of  Silver  Maple,  103;  (4)  Leaf  of 
Lupine,  103. 

EXERCISE  XII 107 

STUDY  OF  SOME  SPECIALLY-MODIFIED  LEAVES:  (1)  Pitcher-plant,  107;  (2) 
Round-leaved  Sundew,  110. 

EXERCISE  XIII 117 

A  TYPICAL  FLOWER  OF  A  DICOTYL:  (1)  Floral  Symmetry,  118;  (2) 
Deviations  from  the  Type,  119:  (a)  Numerical,  119;  (6)  Diminishing  of 
Whorls,  119;  (c)  Increase  in  Number  of  Whorls,  120;  (d)  Growing 
Together  of  Parts,  120;  (e)  Irregularity  of  Parts,  120;  (/)  Deviations 
in  Position  of  Parts,  120. 

EXERCISE  XIV 125 

STUDY  OF  THE  FLOWER  OF  A  RANUNCULACEOUS  PLANT:  (1)  Parts,  125; 

(2)  The  Calyx,  126;  (3)  The  Corolla,  126;  (4)  Floral  Symmetry,  126;  (5) 
Distinctness  of  Parts,  126 ;  (6)  Study  of  Floral  Organs  Individually,  127. 

EXERCISE  XV 131 

STUDY  OF  A  DIMEROUS  FLOWER:  I.  Subterranean  Parts,  131.  II.  Above- 
ground  Parts,  132:  (1)  The  Leaves,  132;  (2)  The  Flower,  132. 


CONTENTS.  7 

PAGE 

EXEKCISE  XVI 137 

STUDY  OF  A  CRUCIFEROUS  FLOWER:  (1)  Anthotaxy,  137;  (2)  Numerical 
Plan  and  Symmetry  of  Flower,  138 ;  (3)  Stamens  and  Pistil,  139. 

EXEKCISE  XVII , 143 

STUDY  OF  A  ROSACEOUS  FLOWER:  (1)  The  Flower,  143;  (2)  The  Calyx, 
143 ;  (3)  The  Corolla,  143 ;  (4)  The  Andrcecium,  144 ;  (5)  The  Gynoe- 
cium,  144. 

EXERCISE  XVIII 149 

STUDY  OF  A  PAPILIONACEOUS  FLOWER  :  I.  External  Characteristics,  149. 
II.  Structure  of  the  Flower,  149  :  (1)  Irregularity,  149;  (2)  Dissymmetry, 
150;  (3)  Cohesion,  150  ;  (4)  Adhesion,  151;  (5,  6,  7)  Drawing,  151 ;  (8) 
Significance  of  Peculiarities  of  Structure,  151. 

EXERCISE  XIX 157 

FLOWER  OF  A  GAMOPETALOUS  DICOTYL  :  (1)  The  Calyx,  157 ;  (2)  The 
Corolla,  157;  (3)  The  Andrcecium,  158;  (4)  The  Gyncecium,  158;  (5) 
Mode  of  Cross-fertilization,  158. 

EXERCISE  XX 163 

STUDY  OF  AN  ERICACEOUS  FLOWER  :  (1)  The  Flowers,  163  ;  (2)  The  Calyx, 
163 ;  (3)  The  Corolla,  164 ;  (4)  The  Androecium,  164 ;  (5)  The  Gynce- 
cium,  165. 

EXERCISE  XXI 169 

STUDY  OF  A  FLOWER  OF  THE  COMPOSITE:  (1)  The  Anthotaxy,  169; 
(2)  The  Involucre,  169;  (3)  The  Flowers,  170:  (a)  The  Common  Recep- 
tacle, 170;  (6)  The  Ray-flowers,  170;  (c)  The  Disk-flowers,  170. 

EXERCISE  XXII 175 

STUDY  OF  A! MONOCHLAMYDEOUS  FLOWER:  (1)  The  Calyx,  176;  (2)  The 
Androecium,  176;  (3)  The  Gynrecium,  176;  (4)  Numerical  Plan  and 
Affinities,  177. 

EXERCISE  XXIII 181 

STUDY  OF  A  LILIACEOUS  FLOWER:  THE  MONOCOTYL  TYPE:  (1)  The 
Anthotaxy,  181;  (2)  The  Prefloration,  181;  (3)  The  Perianth,  182;  (4) 
The  Andro3cium,  182;  (5)  The  Gyncecium,  182;  (6)  Monocotyl  Type 
of  Flower,  183. 

EXERCISE  XXIV 187 

FLOWERS  OF  MONOCOTYLS  (CONTINUED)  :  PART  I.  (1)  The  Perianth,  187; 
(2)  The  Corona,  188;  (3)  The  Andrcecium,  189;  (4)  The  Gynoeciura, 
189.  PART  II.  (1)  The  Sepals,  190;  (2)  The  Corolla,  190;  (3)  The 
Column,  191  ;  (4)  The  Androecium,  191;  (5)  The  Gynoecium,  192;  (6) 
The  Ground  Plan,  192;  (7)  The  Pollination,  192. 


8  CONTENTS. 

PAGE 

EXERCISE  XXV 197 

STUDY  OF  THE  INFLORESCENCE  OF  AN  ABERRANT  MONOCOTYL,  ONE  OF 
THE  ARACEJE:  (1)  The  Anthotaxy,  198;  (2)  The  Flowers,  198:  (a) 
Staminate  Flowers,  198 ;  (6)  Pistillate  Flowers,  198. 

EXERCISE  XXVI 203 

STUDY  OF  FRUITS:  SOME  APOCARPOUS  FRUITS  :  I.  Fruit  of  the  Pea,  204: 
(1)  External  Characteristics,  204;  (2)  Internal  Structure,  205.  II. 
Fruit  of  the  Cherry,  205:  (1)  The  Pericarp,  205;  (2)  Evidence  that 
the  Fruit  is  Apocarpous,  205;  (3)  Internal  Structure,  206;  (4)  The 
Seed,  207. 

EXERCISE  XXVII 211 

STUDY  OF  FRUITS  :  SOME  SYNCARPOUS  FRUITS  :  I.  Fruit  of  the  Poppy,  211 : 
(1)  External  Characteristics,  211;  (2)  Internal  Structure,  212;  (3) 
The  Dehiscence,  212;  (4)  Provision  for  Dispersion,  213.  II.  Fruit  of 
Colchicum,  213:  (1)  External  Characteristics,  213;  (2)  Internal  Structure, 
213;  (3)  Mode  of  Dispersion,  214.  III.  Fruit  of  Hyoscyamus,  214:  (1) 
External  Characteristics,  214;  (2)  Internal  Structure,  214. 

EXERCISE  XXVIII 217 

FURTHER  STUDY  OF  SYNCARPOUS  FRUITS  :  I.  Fruit  of  Coriander,  217. 
II.  Fruil  of  Lemon,  218:  (1)  External  Characters,  218;  (2)  Internal 
Structure,  219. 

EXERCISE  XXIX 223 

STUDY  OF  ACCESSORY  FRUITS:  I.  Wintergreen,  223 :  (1)  External  Charac- 
teristics, 223 ;  (2)  Internal  Structure,  223  ;  (3)  Dispersion,  224.  II.  The 
Fig,  224:  (1)  External  Characteristics,  224;  (2)  Internal  Structure,  224; 
(3)  Mode  of  Dispersion,  225. 

EXERCISE  XXX 229 

STUDY  OF  EXALBUMINOUS  SEEDS:  I.  Almond  Seed,  230:  (1)  External 
Characteristics,  230 ;  (2)  Internal  Structure,  231  ;  (3)  Tests,  231.  II. 
Pumpkin  Seed,  231:  (1)  External  Characteristics,  231;  (2)  Internal 
Structure,  232. 

EXERCISE  XXXI -•">•"> 

STUDY  OF  ALBUMINOUS  SEEDS:  I.  Castor  Sean,  235:  (1)  External  Cha- 
racteristics, 235;  (2)  Internal  Structure,  235.  II.  Black  Pepper  Seed, 
236  :  Internal  Structure,  237. 

EXERCISE  XXXII -241 

STUDY  OF  SEEDS:  MONOCOTYL  AND  DICOTYL  EMBRYOS:  I.  A  Sin  I  ha  ring 
a  Monocotyledonous  Embryo,  241  :  (1)  External  Characteristics,  241  ;  (2) 
Internal  Structure,  242.  II.  A  Seed  having  a  Poly  cotyledon  on* 
244:  (1)  KxtiTiml  Characteristics,  244;  (2)  Internal  Structure,  244. 


CONTENTS. 


PART  II.— VEGETABLE  HISTOLOGY. 

PAGE 

INTRODUCTION 249 

THE  MICROSCOPE  AND  ACCESSORY  APPARATUS  TO  BE  USED  IN  THIS  COURSE, 
249:  The  Microscope,  249:  (1)  The  Stand,  249;  (2)  Optical  Parts,  252; 
(3)  Estimation  of  Magnifying  Power,  253.  Accessory  Apparatus,  255:  (1) 
Stage  Micrometer,  255;  (2)  Section-knife,  255;  (3)  Graduated  Kuler, 
255;  (4)  Dissecting-needles,  255;  (5)  Sharp-pointed  Scissors,  255;  (6) 
Delicate  Forceps  or  Pincettes,  255 ;  (7)  Watch-glasses,  256 ;  (8)  Porcelain 
Evaporating-dish,  256;  (9)  Capped  Keagent-bottles,  256;  (10)  Camel's- 
hair  Brushes,  256;  (11)  Glass  Slides,  256;  (12)  Thin  Cover-glasses,  256. 
Additional  Apparatus:  (a)  Camera  Lucida,  257;  (6)  Polariscope,  257; 
(c)  Draughtsman's  Dividers,  257;  (d)  Microtome,  257;  (e)  Turn-table, 
258.  Micro-Reagents,  258:  Sulphuric  Acid,  258;  Sulphurous  Acid,  259; 
Hydrochloric  Acid,  259 ;  Nitric  Acid,  260 ;  Chromic  Acid,  260 ;  Acetic 
Acid  (Glacial),  260;  Formic  Acid,  261 ;  Picric  Acid,  261;  Osmic  Acid, 
261 ;  Phenol,  or  Carbolic  Acid,  262 ;  Potassium  Hydrate,  262 ;  Potassium- 
Iodide  Iodine,  263;  Chloriodide-of-Zinc  Iodine  Solution,  263;  Chloral 
Hydrate  Iodine,  264;  Sulphuric  Ether,  265;  Mercuric  Chloride,  265; 
Millon's  Reagent,  265 ;  Glycerin,  265 ;  Ammonio-ferric  Alum,  266 ; 
Fehling's  Solution,  266  ;  Labarraque's  Solution,  267 ;  Javelle  Water,  267 ; 
Chloral-Hydrate  Solution,  267 ;  Diphenylamin  Solution,  267 ;  Anilin, 
or  Anilin  Oil,  267  ;  Potassium  Bichromate,  267  ;  Potassium  Ferrocyanide, 
268  ;  Silver  Nitrate,  268 ;  Tannin  Solution,  268 ;  Sodium  Phosphate,  269  ; 
Cuprammonia,  269;  Schulze's  Maceration  Mixture,  269;  Phloroglucin 
Solution,  270;  Anilin  Chloride,  270;  Thymol  Solution,  270;  a-Naphthol 
Solution,  270.  Staining  Fluids,  270:  Grenadier's  Alum  Carmine,  271; 
Ammonia  Carmine,  271 ;  Grenadier's  Hsematoxylin  Solution,  271 ; 
Methyl-green  Solution,  272 ;  Acetic  Methyl-green  Solution,  272 ;  Iodine- 
green  Solution,  272;  Anilin-blue  Solution,  272;  Eosin  Solution,  272; 
Fuchsin  Solution,  273;  Safranin  Solution,  273;  Gentian- violet  Solution, 
273;  Corallin  Solution,  274;  Picric-nigrosin  Solution,  274;  Cyanin 
Solution,  275  ;  Alcannin  Solution,  275.  Permanent  Mounting  or  Enclosing 
Media,  275 :  Canada  Balsam,  or  Balsam  of  Fir,  275 ;  Glycerin  Gelatin, 
275.  Processes  of  Mounting,  276.  Drawing  Microscopic  Objects,  277. 
General  Directions  for  Work,  278. 

EXERCISE  1 283 

THE  TYPICAL  VEGETABLE  CELL,  283. 

EXERCISE  II 291 

TISSUES  OF  THE  HIGHER  PLANTS,  291 :  I.  Transverse  Section,  292.  II. 
Longitudinal  Section,  294. 

EXERCISE  III ! 299 

STUDY  OF  PARENCHYMA,  299 :  I.  Ordinary  Parenchyma  of  Pumpkin  Stem, 
299.  II.  Pitted  Parenchyma  from  Stem  of  Sago  Palm,  301. 


10  CONTENTS. 

PAGE 

EXERCISE  IV 307 

STUDY  OF  COLLENCHYMA,  307  :  I.  Petiole  of  Begonia  Discolor,  307. 

EXERCISE  V 313 

STUDY  OF  SCLEROTIC  PARENCHYMA,  313. 

EXERCISE  VI 319 

STUDY  OF  EPIDERMAL  TISSUE,  319. 

EXERCISE  VII 327 

STUDY  OF  EPIDERMAL  APPENDAGES,  327. 

EXERCISE  VIII 335 

STUDY  OF  SUBEROUS  TISSUE  AND  LENTICELS,  335:  I.  Corky  Tissue,  335. 
II.  Lenticels,  338. 

EXERCISE  IX 345 

STUDY  OF  WOOD-CELLS  OR  LIBRIFORM  TISSUE,  345. 

EXERCISE  X 351 

STUDY  OF  TRACHEARY  TISSUES,  351. 

EXERCISE  XI 357 

STUDY  OF  TRACHEARY  TISSUES  (CONTINUED),  357. 

EXERCISE  XII 367 

STUDY  OF  BAST-FIBRES,  367. 

EXERCISE  XIII 379 

STUDY  OF  SIEVE-TISSUE,  379. 

EXERCISE  XIV 387 

STUDY  OF  L A  TICI  FERGUS  TISSUE,  387. 

EXERCISE  XV 397 

STUDY  OF  STARCHES,  397. 

EXERCISE  XVI 407 

STUDY  OF  ALEURONE-GRAINS,  407. 

EXERCISE  XVII 413 

STUDY  OF  CHLOROPLASTS  AND  COLORING  MATTERS,  413. 

EXERCISE  XVIII 423 

STUDY  OF  INULIN  AND  SUGAR,  423. 


CONTENTS.  11 

PAGE 

EXEKCISE  XIX 429 

STUDY  OF  SECRETION-SACS,  429. 

EXERCISE  XX 439 

STUDY  OF  INTERCELLULAR  AIR-SPACES  AND  SECRETION-RESERVOIRS,  439 

EXERCISE  XXI 447 

STUDY  OF  VASAL  BUNDLES  :  THE  CONCENTRIC  BUNDLE,  447. 

EXERCISE  XXII 457 

STUDY  OF  COLLATERAL  BUNDLES,  457. 

EXERCISE  XXIII 467 

STUDY  OF  RADIAL  BUNDLES,  467. 

EXERCISE  XXIV 477 

STUDY  OF  ROOTS,  477. 

EXERCISE  XXV , 491 

DIFFERENT  TYPES  OF  STEMS,  491 :  I.  The  Fern  Type,  492.  II.  The  Club- 
Moss  Type,  493.  III.  The  Monocotyl  Type,  494.  IV.  The  Dicotyl  Type, 
495. 

EXERCISE  XXVI 503 

STUDY  OF  LEAF  STRUCTURE,  503. 


LABORATORY  EXERCISES  IN  BOTANY. 


GENERAL  INTRODUCTION. 

THIS  work  is  divided  into  two  parts  :  the  first,  which  is  in- 
tended for  beginners,  requires  no  optical  appliances  for  its  suc- 
cessful study  save  the  simple  microscope.  It  deals  mainly  with 
the  gross  structure  of  flowering  plants,  and  includes  the  study  of 
roots,  ordinary  stems,  rhizomes,  tubers,  corms,  bulbs,  leaves, 
flowers,  fruits,  and  seeds.  The  second  part,  which  is  intended 
for  students  somewhat  more  advanced,  requires  the  use  of  the 
compound  microscope.  It  is  devoted  mainly  to  the  study  of  the 
microscopic  structure  of  the  various  organs  of  flowering  plants. 

Each  exercise  is  a  study  as  faithful  and  as  accurate  in  its  de- 
scriptions and  drawings  as  the  author  could  make  it  of  some  por- 
tion of  the  plant-structure.  It  is  expected  that  the  student  will, 
first,  verify  the  facts  stated  and  illustrated  in  the  exercise  by 
observations  of  his  own,  made  according  to  directions,  and  then 
make  an  independent  but  parallel  study  from  some  one  or  more 
of  the  other  plants  named  at  the  opening  of  the  exercise.  In 
doing  this  he  should  by  no  means  neglect  the  drawings.  They 
are  useful  not  only  in  explaining  to  others  the  structures  observed, 
but  they  are  themselves  great  aids  also  to  accurate  observation, 
and  are  equally  helpful  in  giving  vividness  and  permanency  to 
knowledge.  A  structure  that  has  once  been  understood  thor- 
oughly, and  has  been  accurately  drawn,  makes  a  lasting  impres- 
sion upon  the  mind.  The  drawing  need  not  be  elaborate,  the 
time-consuming  work  of  shading  may  often  be  omitted  ;  but  no 
pains  should  be  spared  to  make  it  accurate,  and  all  drawings  for 
scientific  purposes  should  be  made  to  a  definite  scale. 

It  is  hardly  necessary  that  the  student  should  have  had  any 
previous  instruction  in  botany  to  pursue  this  course  successfully, 
though  the  previous  perusal  of  Parts  I.  and  II.  of  the  author's 
College  Botany,  or  of  some  other  book  covering  similar  ground, 

15 


16  LABORATORY    EXERCISES    IN    BOTANY. 

would  be  of  advantage.     Such  a  book,  however,  should  be  con- 
stantly on  hand  during  laboratory-work  for  reference. 

The  glossary  in  the  book  above  referred  to  will  also  be  of  ser- 
vice, for  while  these  exercises  are  not,  it  is  hoped,  overburdened 
with  technical  terms,  it  has  not  been  thought  wise  to  omit  them 
altogether.  If  botany  is  mastered,  its  language  must  also  be 
acquired. 


PART  I. 
ORGANOGRAPHY. 


INTRODUCTION. 

THE  equipment  required  by  the  student  to  pursue  the  course 
of  study  here  laid  down  is  simple  and  inexpensive.  A  good  mag- 
nifying-glass,  a  pair  of  dissecting  needles,  a  sharp  pocket-knife  or 
a  scalpel,  six  glass  slides  and  twice  as  many  cover-glasses  for  tem- 
porarily mounting  sections,  a  camePs-hair  brush  of  medium  size, 
a  rule  with  the  metric  scale  on  one  edge,  a  pair  of  delicate  forceps, 
with  drawing-  and  memorandum-books  and  pencils  for  keeping 
the  appropriate  records  of  observations  made,  are  all  that  are 
really  necessary. 

It  would  be  a  great  advantage,  however,  if  the  student  were  to 
get,  in  place  of  the  ordinary  pocket-magnifier,  a  good  dissecting 
microscope,  so  that  he  may  have  both  hands  free  for  the  work  of 
dissection.  Efficient  instruments  of  this  kind  are  easily  obtain- 
able at  a  moderate  cost  from  many  different  manufacturers  and 
dealers.  The  instrument  shown  in  the  accompanying  cut  is  both 


FIG.  1— Dissecting  Microscope. 

efficient  and  inexpensive.     The  body  consists  of  a  solid  block  of 
hard  wood  so  shaped  that  the  sides  serve  as  hand-rests.      The 

2  17 


18  LABORATORY   EXERCISES   IN   BOTANY. 

stage  is  of  glass,  below  which  is  a  mirror,  fixed  at  an  angle  of  45° 
for  the  illumination  of  a  transparent  object  on  the  stage,  and  there 
is  a  square  rubber  plate,  one  side  of  which  is  white  and  the  other 
black,  to  insert  between  the  mirror  and  the  stage  whenever  white- 
or  dark-ground  illumination  is  required.  The  metallic  lens- 
holder  slides  in  a  brass  tube  driven  into  a  hole  in  the  back  of  the 
block,  into  which  the  cylindrical  column  of  the  holder  nicely  fits, 
rendering  the  lenses  easily  adjustable  for  focus.  The  instrument  is 
provided  with  two  lenses,  which  may  be  used  singly  or  in  combina- 
tion, giving  a  range  of  powers  of  from  five  to  fifteen  diameters. 

The  reagents  employed  are  also  few  and  easily  prepared,  and 
are  as  follows : 

Iodine  Solution. — This  solution  is  thus  prepared  :  Saturate  a 
small  quantity  of  distilled  water  with  potassium  iodide,  and  then 
dissolve  in  it  all  the  iodine  crystals  the  solution  will  take  up,  and 
dilute  with  distilled  water  until  the  liquid  has  a  deep  wine  color. 
This  solution  stains  prbteid  matters  yellowish-brown,  liguified  tis- 
sues a  deep  brown,  cellulose  tissues  scarcely  at  all,  and  starch- 
grains  a  deep  blue.  In  using  the  solution  as  a  test  for  starch  in  sec- 
tions it  is  best  to  dilute  it  with  four  or  five  times  its  bulk  of  water, 
otherwise  the  grains  will  be  so  deeply  stained  as  to  appear  black. 

Another  method  of  detecting  the  presence  of  starch  in  vegetable 
structures  is  to  boil  for  a  few  moments  some  fragments  of  the  tis- 
sue to  be  tested  in  a  few  cc.  of  distilled  water  in  a  test-tube,  and 
then,  after  the  solution  has  cooled,  drop  in  a  little  of  the  strong 
solution,  when,  if  starch  is  present,  the  decoction  will  immediately 
acquire  a  blue  color,  the  depth  of  which  will  depend  on  the  quan- 
tity of  starch  present.  On  boiling  the  solution  the  blue  color  dis- 
appears, to  reappear  when  cooling  takes  place. 

Potassium  Hydrate. — To  prepare  this  reagent  make  a  10  per 
cent,  solution  of  the  pure  fused  potassium  hydrate  in  distilled 
water,  and  keep  it  in  well-stopped  bottles.  If  corks  are  used, 
they  should  be  paraffined,  and  if  glass-stoppered  bottles  are 
employed,  the  stoppers  should  first  be  smeared  with  vaseline  to 
prevent  their  sticking.  This  solution  is  useful  as  a  clearing  airmt, 
since  it  rapidly  dissolves  the  proteids  and  starch  and  saponifies 
and  dissolves  fats.  It  also  stains  corky  tissues  yellow  or  yellow- 
ish-brown, e-jx'ciallv  when  warmed  in  contact  with  them,  and 
tannin  cells  are  also  colored  yellow  or  brown  by  it,  though  a  better 


INTRODUCTION.  19 

test  for  tannin  is  a  solution  of  some  ferric  salt.  For  clearing, 
the  chloral-hydrate  solution  recommended  in  the  Introduction  to 
Part  II.  may  be  used  instead,  and  in  many  cases  is  superior. 

Ferric  Chloride. — This  solution  is  prepared  by  dissolving  about 
5  grammes  of  ferric  chloride  in  50  cc.  of  distilled  water  and  add- 
ing a  drop  of  nitric  acid.  The  solution  should  be  renewed  from 
time  to  time.  A  drop  of  this  solution  applied  to  a  section  con- 
taining  tannic  matters  will  produce  a  bluish-black  or  a  greenish- 
black  precipitate,  according  to  the  variety  of  tannin  that  is  pres- 
ent. Rarely,  however,  other  substances  present  may  produce 
similar  precipitates  with  this  reagent.  Instead  of  this,  there 
may  be  employed,  with  equal  advantage,  the  ferric-alum  solution 
described  in  the  Introduction  to  Part  II. 

Phloroglucin  Reagent. — This  reagent  consists  of  two  liquids, 
which  are  to  be  kept  in  separate  bottles  :  (1)  a  5  per  cent,  solution 
of  phloroglucin  in  95  per  cent,  alcohol,  and  (2)  strong  hydrochloric 
acid.  This  is  one  of  the  most  useful  reagents,  and  is  employed 
for  distinguishing  between  lignified  and  unlignified  tissues.  The 
test  is  applied  as  follows  :  To  a  section  of  the  tissue  to  be  studied 
apply  first  a  drop  or  two  of  the  phlorogluciu  solution,  and  then, 
after  a  few  moments,  a  similar  quantity  of  the  hydrochloric  acid. 
If  any  lignified  tissues  are  present,  they  will  be  stained  red,  while 
unlignified  ones  remain  unstained.  The  arrangement  of  the  bun- 
dles and  that  of  bast-fibres  and  stone-cells  may  thus  be  traced 
with  little  difficulty. 

Alcannin  Solution. — This  reagent  is  prepared  by  adding  to  a 
solution  of  alcauniu  in  absolute  alcohol  an  equal  bulk  of  distilled 
water  and  then  filtering  it.  It  colors  fats,  volatile  oils,  and 
resins  a  deep  red,  and  hence  is  a  most  convenient  test  for  the  pres- 
ence of  these  bodies.  The  best  results  are  obtained  by  letting  sec- 
tions soak  in  the  solution  for  two  hours  or  more.  (See  also  Intro- 
duction to  Part  II.) 

Preparation  of  Dried  Material  for  Study. — Many  dried  mate- 
rials, such  as  some  medicinal  roots,  rhizomes,  etc.,  may  be  studied 
quite  satisfactorily  in  the  dried  form  by  making  longitudinal  and 
transverse  sections  and  applying  the  appropriate  tests.  But  more 
frequently  the  dried  material  is  too  hard,  too  friable,  or  too  brittle 
to  be  satisfactorily  studied  in  this  way,  and  some  preliminary 
treatment  is  necessary. 


20  LABORATORY    EXERCISES   IN   BOTANY. 

Except  in  the  case  of  very  hard  tissues  the  following  treatment 
is  usually  satisfactory  :  First  soak  the  specimen  in  alcohol  to  expel 
the  air ;  then  (2)  in  water  for  a  few  hours  until  thoroughly  per- 
meated by  the  liquid  ;  and  then  (3),  if  the  tissues  are  too  soft  for 
satisfactory  sectioning,  as  is  frequently  the  case,  particularly  with 
herbaceous  or  succulent  specimens,  they  should  be  hardened  by 
immersion  for  at  least  twenty-four  hours  in  strong  alcohol.  If 
now  too  hard  or  too  brittle  for  cutting,  they  should  be  immersed 
in  a  mixture  of  equal  parts  of  alcohol  and  glycerin  for  twenty- 
four  hours. 

According  to  the  author's  experience,  the  great  majority  of 
specimens  of  roots,  rhizomes,  tubers,  corms,  fruits,  and  seeds 
yield  the  best  results  when  carried  through  all  the  stages  of  the 
process  above  described. 

In  the  case  of  structures  which,  like  gentian  root,  for  example, 
have  shrunken  much  in  the  process  of  drying,  it  is  necessary,  in 
order  to  restore  them  to  their  natural  dimensions,  to  modify  the 
second  stage  in  the  above  process  by  using  alkaline  instead  of  pure 
water.  A  1  per  cent,  solution  of  potassium  hydrate  in  distilled 
water  is  suitable  for  most  cases.  Before  hardening  in  alcohol  it  is 
advisable  to  wash  out  the  alkali  by  means  of  pure  water. 

In  the  case  of  very  hard  tissues,  such  as  shells  of  nuts,  etc., 
softening  is  also  effected  by  the  use  of  the  alkaline  solution.  The 
strength  of  the  solution  employed  will  depend  somewhat  on  the 
nature  of  the  tissues,  but,  as  a  usual  thing,  weak  solutions,  1  or  2 
per  cent.,  are  preferable  to  strong  solutions.  In  some  instances  an 
immersion  for  several  days  will  be  required  to  effect  the  proper 
degree  of  softening.  After  this  has  been  effected  the  tissues  should 
be  washed  to  get  rid  of  the  alkali,  and  then  be  transferred  to 
glycerin,  or  to  a  mixture  of  equal  parts  of  glycerin  and  alcohol, 
preparatory  to  sectioning. 

In  the  case  of  dried  leaves,  flowers,  or  herbarium  specimens, 
which  it  is  desired  to  restore  as  nearly  as  possible  to  the  condition 
of  fresh  specimens,  it  is  usually  sufficient  to  immerse  them  for  a 
few  hours  either  in  1  per  cent,  potassium-hydrate  solution  or  in  a 
weak  solution  of  ammonium  hydrate. 

Examining  Sections. — Explicit  directions  for  sectioning  are 
given  in  the  Introduction  to  Part  II.,  to  which  the  student  is 
referred.  For  the  purposes  of  study  by  means  of  the  simple 


INTRODUCTION.  21 

microscope  it  is  not  usually  necessary  to  make  sections  so  thin 
that  they  will  freely  transmit  light ;  but  it  is  necessary  that  they 
be  made  of  nearly  even  thickness,  and  made  with  a  very  sharp 
knife,  so  that  the  tissues  are  not  torn  nor  displaced. 

For  the  purposes  of  this  course  two  different  kinds  of  sections 
are  usually  necessary — one  transverse,  and  the  other  longitudinal 
— and  great  care  should  be  taken  that  the  former  are  strictly  trans- 
verse or  directly  across  the  grain,  and  that  the  latter  are  strictly 
longitudinal.  Oblique  sections  are  worthless. 

Immediately  after  cutting  a  section  it  should  be  transferred  to 
water  or  to  other  liquid  to  prevent  the  entrance  of  air-bubbles, 
which  obstruct  the  view  of  the  structure,  and  which,  having  once 
entered,  are  very  difficult  to  get  rid  of. 

When  sections  are  tested  they  should  be  transferred  to  a  glass 
slide,  and  for  study  they  should  always  be  mounted  in  water, 
glycerin,  or  some  other  transparent  liquid  on  a  glass  slide,  and 
be  covered  with  a  cover-glass ;  otherwise  the  object  will  appear 
more  or  less  distorted. 

Care  of  Reagents  and  Apparatus. — The  reagents  are  best  kept 
in  glass-capped  bottles,  such  as  those  illustrated  in  the  Introduc- 
tion to  Part  II.  Each  bottle  should  contain  a  small  glass  tube 
to  be  used  for  transferring  a  few  drops  of  the  solution  to  the 
object  to  be  tested,  and  great  care  should  be  exercised  not  to  mix 
and  spoil  the  reagents  by  putting  the  tubes  into  the  wrong  bottles. 
The  student  should  bear  in  mind  that  some  of  the  reagents 
employed  are  corrosive,  and  therefore  should  be  on  his  guard 
against  using  them  in  a  way  that  will  injure  his  apparatus. 

Whenever  it  is  necessary  to  clean  the  lenses  of  the  microscope, 
this  should  be  done  by  means  of  a  clean  linen  or  a  cotton  cloth, 
or,  better,  by  means  of  Japanese  filter-paper,  otherwise  the  lenses 
will  be  liable  to  be  scratched  or  their  polish  impaired,  to  the 
detriment  of  their  optical  efficiency. 

To  reduce  the  labor  of  description  to  a  minimum,  and  at  the 
same  time  to  ensure  method  and  thoroughness,  forms  for  the 
description  of  roots,  stems,  leaves,  flowers,  fruits,  and  seeds  have 
been  inserted  at  the  close  of  these  subjects  respectively.  These 
forms  are  also  printed  in  separate  record-books  for  the  use  of 
students. 


EXERCISE  I. 

STUDY  OF  EOOTS. 

SOME  or  all  of  the  roots  of  the  following  plants  may  be  studied  : 
Dandelion  (Taraxacum  officinale,  Weber),  Yellow  Dock  (Rumex 
crispus,  L.),  Burdock  (Arctium  Lappa,  L.\  Carrot  (Daucus  Carota, 
L.),  Radish  (Raphanus  Rhaphanistrum,  L.\  Salsify  (Tragopogon 
porrifolius,  L.),  Maize  (Zea  Mays,  L.\  Smilax  (Smilax  rotundi- 
folia,  L.)\  Duckweed  (Lemna  polyrrhiza,  L.),  and  English  Ivy 
(Hedera  helix,  L.). 

There  is  selected  for  the  first  study  the  root  first  mentioned, 
that  of  Dandelion.  In  removing  it  from  the  soil  care  should  be 
taken  that  the  root  system  be  obtained  as  nearly  uninjured  and 
complete  as  possible.  The  plant  should  be  taken  up  with  an 
abundance  of  earth,  and  the  latter  washed  away  by  holding  it  in 
a  gentle  stream  of  water,  so  that  the  finer  branches  may  not  be 
broken.  Having  obtained  a  satisfactory  specimen,  observe — 

I.  THE  EXTERNAL  CHARACTERISTICS. — (1)  Parts. — The 
upper  or  ringed  portion,  from  which  the  leaves  spring  or  which 
shows  the  scars  of  leaves  that  have  withered  and  disappeared, 
differs  not  only  in  appearance,  but,  as  will  presently  be  shown, 
also  in  internal  structure,  from  the  rest.  It  is,  in  fact,  a  stem, 
and  not  a  part  of  the  root.  One  of  the  characteristic  differ- 
ences between  a  root  and  a  stem  is  that  the  latter  bears  leaves 
in  some  form,  while  the  former  does  not.  This  stem,  of  which 
the  root  proper  is  the  downward  continuation,  is  technically  called 
the  crown.  In  the  present  instance,  and  in  the  roots  of  many 
other  biennial  or  perennial  herbs,  the  crown  is  liable  to  separate 
into  several  branches,  each  bearing  a  tuft  of  leaves.  These 
branches  are  often  called  heads,  and  the  root  is  then  said  to  be 
many-headed.  The  junction  of  the  crown  with  the  root  proper 
is  termed  the  neck.  In  the  Dandelion,  and  in  very  many  other 
plants,  but  by  no  means  in  all,  the  root  appears  to  be  a  downward 
prolongation  of  the  stem.  Such  a  root  is  called  a  primary  root, 

23 


24  LABORATORY    EXERCISES    IN    BOTANY. 

in  distinction  from  one  that  springs  out  laterally  from  a  stem,  and 
which  is  called  secondary  or  adventitious.  Of  the  latter  sort  are 
the  climbing  rootlets  of  Poison  Rhus,  the  air-roots  of  the  Ban- 
yan, etc.  Also,  if,  as  in  the  Dandelion,  the  main  root  does  not 
almost  immediately  break  up  into  smaller  ones,  but  maintains  its 
ascendency  over  its  branches  until  it  reaches  a  considerable  depth 
in  the  ground,  it  is  called  a  tap-root. 

On  Plate  I.  (Fig.  1),  a  is  one  of  the  heads,  b  and  c  annular 
markings  on  the  crown,  and  just  below  c  is  the  neck. 

(2)  Shape. — The  shapes  of  Dandelion  roots  vary  considerably 
among  themselves,  but  that  of  the  one  in  the   figure  may  be 
described  as  conical,  since  it  tapers  gradually  from  the  crown 
downward. 

(3)  Kind. — As  above  stated,  the  root  is  primary  and  a  tap-root. 

(4)  Branches  and  Other  Appendages. — The  main  root  frequently 
gives  off  one  or  more  large  branches,  and  always  a  multitude  of 
smaller  ones,  and  all  these  branches  occur  without  definite  order, 
as  is  frequently,  though  not  always,  the  case  with  roots.     In  the 
Radish,  for  example,  the  branches  occur  mostly  in  two  vertical 
rows  on  opposite  sides  of  the  main  root. 

It  will  be  observed  that  the  rootlets  break  up  into  finer  and 
finer  divisions,  until  the  ultimate  ones  are  quite  minute,  thus 
exposing  a  very  considerable  absorbing  surface  to  the  soil.  This 
surface  is  still  further  greatly  increased  by  the  presence  of  vast 
numbers  of  root-hairs,  which  thickly  clothe  all  the  finer  divisions 
of  the  root.  In  fact,  these  hairs,  rather  than  the  roots  themselves, 
are  the  chief  agents  for  absorbing  nutriment  from  the  soil.  Some 
of  them  may  readily  be  seen  with  a  hand-magnifier  or  even 
with  the  naked  eye,  but  unless  the  roots  have  been  separated  from 
the  soil  with  extreme  care  they  are  mostly  destroyed.  They  may 
be  made  to  form  again  in  great  numbers,  however,  if,  after  remov- 
ing the  plant  from  the  ground  and  washing  it,  the  roots  are  kept 
for  two  or  three  days  in  a  warm,  moist,  and  dark  chamber. 

Exceptionally,  roots  bear  buds,  which  may  give  rise  to  new 
stems,  but  adventitious  buds  of  this  kind  seldom  if  ever  occur  on 
Dandelion  roots. 

(5)  Markings. — Tuberculose  or  papillose  markings  may  often  be 
observed  on  the  main  root  or  on  its  larger  branches,  from  which 
rootlets  formerly  issued,  but  have  since  disappeared.     Frequently 


STUDY   OF    ROOTS.  25 

also  rough  corky  patches,  caused  by  wounds  that  have  healed  or 
are  in  the  process  of  healing,  may  be  seen. 

(6)  Color. — The  color  of  the  uninjured  root  is  usually  light- 
brown  or  yellowish-brown  in  the  younger,  becoming  darker  in 
the  older,  portions.     This  color  resides  in  the  corky  outside  layer. 

(7)  Measurements  should  also  be  made  of  the  roots  studied, 
recording  the   length   and  greatest  thickness.     The  one  figured 
above,  for  example,  has  a  length  of  about  18  cm.  and  a  maxi- 
mum thickness  of  about  1  cm.,  wrhile  that  of  the  crown  is  about 
1J  cm. 

(8)  The   student   should   now    make   a   drawing  of  the   root 
which  he  is  studying,  indicating  by  aid  of  letters  and  lines  the 
important  structural  points,  as  suggested  in  the  model  drawing 
(PL  I.  Fig.  1). 

II.  THE  INTERNAL,  STRUCTURE. — The  internal  structure 
should  be  studied  by  making  transverse  and  longitudinal  sec- 
tions, and  applying  to  them  such  reagents  as  are  necessary  to 
reveal  their  structure  more  distinctly,  and  by  examining  them 
with  a  magnifying-glass. 

(1)  Transverse  Section  of  Root. — Make  two  or  three  transverse 
sections,  one  just  below  the  crown,  the  others  lower  down.  They 
will  differ  in  size,  but  it  will  be  observed  that  they  have  substan- 
tially the  same  structure,  except  that  possibly  a  small  pith  may 
be  found  in  or  near  the  centre  of  the  upper  one,  but  not  in  the 
others.  The  central  yellowish  portion,  not  more  than  about  one- 
fourth  the  diameter  of  the  entire  section,  is  called  the  woody 
cylinder  or  meditullium.  Surrounding  this  cylinder  is  the  thick 
white  bark,  composed  of  softer  tissues,  from  which,  when  fresh, 
there  oozes  a  copious  white  milk-juice.  This  fluid,  it  will  be 
observed,  does  not  issue  from  the  meditullium.  The  zone  of 
junction  between  the  meditullium  and  the  bark  constitutes  the 
cambium  zone,  in  which,  in  the  roots  and  stems  of  gymnosperms 
and  dicotyls  during  the  growing  season,  increase  in  thickness 
takes  place  by  the  formation  of  new  cells.  To  the  naked  eye  or 
under  an  ordinary  magnifier  the  cambium  looks  like  a  mere  line, 
but  it  really  consists  of  several  layers  of  small  very  thin-walled 
cells. 

The  bark  really  consists  of  three  layers.  The  outer,  called 
the  epiphlosum,  is  the  thin,  brownish,  corky  covering  of  the  root ; 


26  LABORATORY    EXERCISES    IN   BOTANY. 

the  middle  and  inner  layers  are  called  respectively  the  mesophlceum 
and  the  endophlceum.  In  many  roots  these  two  layers  appeal*  quite 
distinct  to  the  eye,  but  in  the  Dandelion  their  similarity  in  appear- 
ance is  too  close  for  this,  and  they  can  only  be  delimited  clearly 
by  aid  of  the  compound  microscope.  With  a  magnifying  power 
of  about  fifty  diameters  the  inner  bark  shows  a  radial  structure 
which  the  middle  bark  does  not  possess. 

The  milk-vessels  are  confined  to  these  two  layers,  and  their 
distribution  in  this  root  is  quite  peculiar.  Observation  shows 
that  they  are  grouped  in  interrupted  concentric  circles  (PI.  I. 
Fig.  3).  The  ringed  appearance  of  the  cross-section,  observable 
even  in  the  dried  root,  is  due  to  this. 

In  the  roots  of  most  biennial  and  perennial  dicotyls,  and  in 
those  of  gymuosperms,  the  meditullium  shows  a  distinct  radial 
structure  consisting  of  medullary  rays  running  from  the  centre 
across  the  cambium  zone  to  the  limits  of  the  inner  layer  of  the 
bark,  and  separating  the  wood  into  wedge-shaped  bundles.  This 
structure  is  present  in  the  Dandelion  root,  though  impossible  to 
trace  without  the  aid  of  a  compound  microscope.  But  no  such 
structure  exists  in  the  roots  of  monocotyls. 

(2)  Longitudinal  Section. — This  section,  if  made  through  the 
centre  of  the   root,  shows  that  the   meditullium  is  a   ligneous 
cylinder  extending  from  one  end  of  the  root  to  the  other.     More- 
over, it  sends  branches  not  only  into  the  larger,  but  also  into  all 
the  finer,  subdivisions  of  the  root. 

(3)  Tests. — Certain  reagents  applied  to  the  sections  will  enable 
one  to  learn  some  additional  facts  about  the  structure. 

(a)  The  Iodine  Test. — The  thick,  fleshy  root  evidently  has 
stored  within  it  much  nutritive  matter,  to  which  is  due  the  rapid 
unfolding  of  the  leaves  and  flowers  in  the  spring.  Is  a  part  of 
this  food-material  in  the  form  of  starch  or  not?  The  iodine  test 
will  answer  the  question.  Applying  a  drop  of  potassium-iodide 
iodine  to  a  cross-section,  only  a  yellowish-brown  color  is  produced. 
Had  starch  been  present  the  reagent  would  have  produced  im  me- 
diately a  deep-blue  color,  appearing  almost  black  if  the  solution 
used  were  a  strong  one.  Whatever  food-materials  may  be  present, 
then,  starch  is  certainly  not  one  of  them,  widely  distributed  as 
this  substance  is  in  the  vegetable  world.  The  fact  is,  that  in  this 
plant,  and  in  most  others  of  the  natural  order  to  which  it  belongs, 


STUDY   OF    ROOTS.  27 

the  Composite,  a  related  substance,  inulin,  which  does  not  react 
blue  with  iodine,  replaces  starch  as  a  reserve  food-material. 

Observing  more  closely  the  color-changes  produced  in  the  speci- 
men by  the  iodine,  it  is  found  that  the  white  tissues  of  the  middle 
and  inner  bark  have  acquired  a  light  yellowish-brown  color, 
while  the  tissues  of  the  meditullium  have  been  stained  a  deep 
yellowish-brown.  The  color  of  the  former  is  chiefly  due  to  the 
presence  of  albuminous  matters  in  the  bark-cells,  while  that  of 
the  latter  is  caused  by  the  presence  of  lignin  or  woody  matter  in 
the  cell-walls  of  the  meditullium.  It  is  thus  learned  that  the 
iodine  stains  albuminous  substances  light  yellowish-brown,  ligni- 
fied  cell-walls  deep  yellowish-brown,  and  the  walls  of  ordinary 
thin-walled  cells  scarcely  at  all. 

(6)  The  Phlorogludn  Test. — To  a  fresh  cross-section  apply  first 
two  or  three  drops  of  a  5  per  cent,  alcoholic  solution  of  phloro- 
gluciu,  and,  after  a  few  moments,  two  or  three  drops  of  strong 
hydrochloric  acid.  Presently  a  deep-red  color  will  be  developed 
in  the  meditullium,  while  the  rest  of  the  section  will  remain 
wholly  unstained.  Since  this  reagent  stains  no  tissues  red  except- 
ing lignified  ones,  it  confirms  one  of  the  results  obtained  by  the 
iodine  test.  This  test  is  of  great  value  in  the  investigation  of 
roots  and  stems,  for  it  often  beautifully  differentiates  structures 
which  without  its  aid  might  not  easily  be  distinguished. 

(c)  The  Ferric-chloride  Test. — If  tannic  matters  occur  in  tis- 
sues, the  fact  is  revealed  by  applying  a  little  of  this  reagent  to 
a  section,  when  a  greenish-black  or  bluish-black  precipitate 
will  be  produced.  Other  than  tannic  matters,  however,  capa- 
ble of  similar  reactions  with  ferric  chloride,  sometimes  occur  in 
plants,  so  one  should  be  cautious  about  drawing  conclusions  based 
on  this  test  alone.  But  the  test  is  of  value  in  another  way.  If 
tannic  or  other  matters  producing  a  precipitate  be  present,  their 
greater  abundance  in  some  tissues  than  in  others,  or  their  total 
absence  in  some  and  abundance  in  others,  are  often  a  means 
of  revealing  structure  more  clearly;  for  example,  by  bringing 
the  medullary  rays  into  greater  prominence,  rendering  the  bark 
more  distinct  from  the  wood,  or  the  cambium  zone  more  con- 
spicuous. 

In  the  present  case,  however,  a  drop  of  the  reagent  applied  to 
the  surface  of  a  fresh  section  produces  scarcely  any  change  of 


28  LABORATORY    EXERCISES   IN   BOTANY. 

color.      Dandelion   root,   therefore,   ordinarily  at   least,  contains 
little  if  any  tannin. 

(4)  Drawing. — On  a  scale  large  enough  clearly  to  indicate  the 
important  points  in  the  structure  make  a  drawing  of  the  trans- 
verse section,  indicating  the  different  parts  by  aid  of  letters  and 
lines  as  suggested  on  Plate  I.  (Fig.  3). 

(5)  Transverse  Section  of  the  Crown. — Make  two  or  three  trans- 
verse sections  at  different  levels,  and  compare  them  carefully  with 
the  ones  already  studied  of  the  root.     It  will  be  observed  that  the 
woody  cylinder  is  relatively  thicker  than  in  the  latter ;  that  it  has 
a  distinct  pith ;  that  the  radial  structure  of  the  meditullium  is 
much  more  distinct  than  in  the  root ;  and  that  these  differences 
are  more  conspicuous  a  few  millimetres  above  and  below  the  neck 
than  they  are  near  it,  where  there  is  a  gradual  transition  of  one 
organ  into  the  other.     Draw  a  diagram  of  one  of  the  cross-sec- 
tions and  indicate  the  parts,  as  in  Figure  2  (PI.  I.). 

If  the  tips  of  any  one  of  the  hundreds  of  small  root-branches 
of  the  Dandelion  were  examined  under  a  compound  microscope, 
each  would  be  found  to  possess  a  cap  of  older  and  thicker-walled 
cells,  whose  function  it  is  to  protect  the  growing  point,  which  lies 
a  little  way  back  of  the  apex,  during  the  movements  of  the  root- 
lets through  the  soil.  The  structure  is  shown  in  Figure  4  (PI.  I). 
This  protective  covering  is  called  the  root-cap.  In  some  plants, 
as  the  Duckweeds  (Lemua  minor  and  L.  polyrrhiza),  it  is  large 
enough  to  be  seen  easily  with  the  naked  eye. 

Now,  in  a  similar  manner,  study,  describe,  and  figure  one  of 
the  five  following  roots :  Yellow  Dock,  Burdock,  Carrot,  Radish, 
or  Salsify,  all  dicotyls,  and  afterward  compare  the  selected  root 
carefully  with  the  roots  of  Maize  or  of  Srnilax,  which  are  mono- 
cotyls.  Note  carefully  all  the  important  points  of  difference  in 
structure  and  habit. 


STUDY   OF   ROOTS. 


29 


a 


~e 


in 

: 


PLATE  I.,  FIG.  1.— Root  of  Dandelion  (%  natural  size) :  a,  one  of  the  heads ;  b,  an- 
nular markings;  c,  annular  marking  immediately  above  the  neck  of  the  root;  d,  one 
of  the  larger  root-branches ;  e,  one  of  the  finer  branches  or  fibrils. 

FIG.  2.— Diagram  of  Cross-section  of  the  Crown   (magnified  1^  diameters) :  a,  corky 
yer  of  the  bark :  c,  circularly  arranged  milk-vessels ;  d,  woody  cylinder  crossed  by  med- 
ullary rays  and  containing  a  pith,  e,  in  the  centre. 

FIG.  3.— Diagram  of  the  Cross-section  of  the  Main  Root  a  little  below  the  neck  (magni- 
fied 1%  diameters) :  a,  corky  layer  of  bark  ;  c,  concentrically  arranged  milk-vessels ; 
d,  central  cylinder. 

FIG.  4.— Tip  of  Small  Root  (magnified  about  50  diameters),  showing  growing-point  (a) 
and  root-cap  (6). 


FOKM  FOE  STUDY  OF  ROOTS. 


I.  KIND. 

3.  Agreeable. 

c.  Mesophloeum. 

1.  Primary. 

4.  Aromatic. 

Stone-cells. 

2.  Adventitious. 

5.  Mint-like. 

Numerous. 

II   FORM 

6.  Balsamic. 

Few. 

1.  Simple. 
2.  Branching. 
3.  Conical. 

7.  Camphoraceous. 
8.  Terebinthinous. 
9.  Pungent. 

d.  Endophloeum. 
Distinctly  radiate. 
Indistinctly    " 

4.  Fusiform. 
5.  Napiform. 
6.  Fasciculate 

10.  Musky. 
11.  Disagreeable. 
12.  Irritating. 

Not  radiate. 
Bast-masses. 
Stratified. 

7.  Fibrous. 

13.  Nauseous. 

Unstratified. 

14.  Narcotic. 

Shape 

III.  SIZE. 

15.  Putrid. 

Conical 

1.  Length. 

16.  Fetid. 

Linear 

2.  Greatest  thickness. 

IV.  COMPOSITION. 

X.  INTERNAL  STRUCTURE. 

Oblique. 
Curved. 

1.  Many-headed. 
2.  Few-headed. 

1.  Monocotyl  type. 
(1)  Cylinder-sheath. 

Bast-fibres. 
Numerous. 

3.  Single-headed 

V.  MARKINGS. 
*1.  Annulate. 
2.  Warty. 
3.  Wrinkled. 

a.  Distinct. 
b.  Indistinct, 
c.  Lignified. 
d.  Unlignified. 
(2)  Cortex, 
a.  Thickness  comparec 

Few.           [fied. 
Strongly    ligni- 
Slightly 
Unlignified. 
(3)  Woody  cylinder, 
a.  Distinctly  radiate. 

4.  Keeled. 
5.  Fissured. 

with  central  cyl 
inder. 

b.  Indistinctly  radiate, 
c.  Annulate. 

Transversely. 
Longitudinally. 

6.  Bundles  in  : 
Numerous. 

d.  Medullary  rays. 
Narrow. 

VI.  FRACTURE. 

Few  or  none. 

Medium. 

1.  Short. 

Lignified. 

Broad. 

2.  Brittle. 

Unlignified. 

Lignified. 

3.  Splintery. 

(3)  Central  cylinder. 

Unlignified. 

4.  Fibrous. 

a.  Rays  in  : 

e.  Xylem  wedges. 

5.  Horny. 

Numerous. 

Narrow. 

6.  Corky. 

Few. 

Medium. 

7.  Mealy. 

Lignified. 

Broad. 

8.  Friable. 

Unlignified. 

Lignified. 

VII.  COLOR. 

(4)  Starch, 
a.  Most    abundant    in 

Unlignified. 
/.  Ducts. 

1.  Exterior. 
2.  Interior. 

cortex. 
b.  Most    abundant    in 

Conspicuous. 
Inconspicuous. 

VIII.  TASTE. 

central  cylinder. 

Numerous. 

L  Insipid. 

(5)  Tannic  matters. 

Few. 

2.  Bland. 

a.  Most    abundant    in 

g.  Fissuring. 

3.  Sweet. 

cortex. 

Fissured. 

4.  Bitter. 

6.  Most   abundant   in 

Entire. 

5.  Mucilaginous. 
6.  Pungent. 

central  cylinder. 
2.  Dicotyl  type. 

(4)  Starch, 
a.  Most  abundant  in— 

7.  Acrid. 

(1)  Cambium  zone. 

Mesophloeum. 

8.  Warm. 

a.  Distinct. 

Endophloeum. 

9.  Cooling. 

6.  Indistinct. 

Medullary  rays. 

10.  Astringent. 

(2)  Bark. 

Xylem  wedges. 

11.  Nauseous.      • 

a.  Thickness    relative 

6.  No  starch. 

12.  Burning. 

to  wood. 

(5)  Tannic  matters. 

13.  Prickling. 

b.  Layers. 

a.  Most  abundant  in  — 

14.  Saline. 

Indistinct. 

Exophlceum. 

15.  Alkaline. 

Distinct. 

Mesophlceum. 

16.  Acidulous. 

Relative  thickness 

Endophloeum. 

of— 

Cambium  zone. 

IX.  ODOR. 

Exophloeum. 

Medullary  rays. 

1.  Odorless. 

Mesophloeum. 

Xylem  wedges. 

2.  Faint. 

Endophloeum. 

i 

b.  No  tannic  matters. 

EXERCISE  II. 

STUDY  OF  STEMS. 

SOME  or  all  of  the  following  stems  may  be  studied :  Twigs  of 
Hickory  (Carya  alba,  Nutt.\  Horse-chestnut  (yEsculus  Hippo- 
castanum,  L.),  Balsam  Poplar  (Populus  balsamifera,  L.\  Ash 
(Fraxinus  Americana,  L.\  Lilac  (Syringa  vulgaris,  L.),  Maple 
(Acer  dasycarpum,  Ehrh.\  Basswood  (Tilia  Americana,  L.),  the 
climbing  stems  of  Green  Briar  (Smilax  rotund ifolia,  L.),  and  the 
herbaceous  stems  of  Sunflower  (Helianthus  annuus,  L.),  and 
Maize  (Zea  Mays,  L.). 

Let  there  first  be  examined  carefully  a  twig  of  the  common 
Shell  bark  Hickory,  and  the  study  of  this  will  form  a  basis  for 
the  study  of  the  rest.  Any  well-developed  twig  of  the  tree,  rep- 
resenting a  growth  of  at  least  two  years  and  gathered  late  in 
autumn  or  in  early  spring  before  the  leaves  unfold,  will  serve  the 
purpose. 

I.  THE  EXTERNAL  CHARACTERISTICS. — Parts  and  Mark- 
ings.— (1)  At  the  apex  or  upper  end  of  the  twig  is  observed  a 
large  scaly  bud  called  the  terminal  bud.  Below  this,  at  inter- 
vals along  the  stem,  are  other  buds,  smaller  in  size,  but  otherwise 
similar.  These  buds,  since  they  occur  just?  above  where  the  leaf 
of  the  previous  season  joined  the  stem,  are  called  axillary  buds. 
The  heart-shaped  scar  caused  by  the  fall  of  the  leaf  may  be  seen 
immediately  below  the  bud  in  each  case.  These  buds  and  leaf- 
scars,  it  should  be  observed,  are  not  arranged  without  order,  but 
in  a  regular  spiral  about  the  stem. 

If  the  twig  has  had  a  rapid  growth,  we  are  liable  to  find  more 
than  one  bud,  sometimes  as  many  as  three,  in  or  near  the  leaf- 
axil.  In  the  Hickory  these  buds  are  arranged  one  above  the 
other,  the  smallest  nearest  the  leaf-scar,  the  next  larger  just  above 
this,  and  the  largest  most  remote  from  the  scar.  The  real  axillary 
bud  is  the  first  mentioned  and  smallest ;  the  others  are  called  super- 
numerary  buds. 

31 


32  LABORATORY    EXERCISES   IN   BOTANY. 

In  some  other  members  of  the  Walnut  family,  to  which  the 
Hickory  belongs — as,  for  example,  the  Bitternut  Hickory — these 
vertically  arranged  supernumerary  buds  are  nearly  always  pres- 
ent. A  more  common  arrangement  of  these  buds  is  seen  in  the 
Red  Maple,  the  Tartarian  Honeysuckle,  and  the  wild  Black  Cur- 
rant, where  the  supernumeraries  occur  alongside  of  or  on  the  same 
level  with,  and  not  above,  the  axillary  bud. 

(2)  Some  distance  down  the  twig  from  the  terminal  bud  will 
be  seen  a  series  of  closely-arranged,  ring-like  scars.     These  mark 
the  position  of  the  terminal  bud  of  the  previous  year ;  they  are, 
in  fact,  the  scars  left  by  the  falling  off  of  its  scales.     They  are 
indicated  at  /  in  Figure  I  (PI.  II.). 

(3)  Minute  dots,  slight  elevations  in  its  corky  exterior  layer, 
may  also  be  seen  freely  sprinkled  over  the  surface  of  the  twig. 
These  dots  are  called  lenticels,  and  are  probably  serviceable  in  the 
respiration  of  the  plant.     Their  structure  cannot  well  be  under- 
stood without  the  aid  of  a  compound  microscope. 

(4)  Enough  of  the  twig  which  the  student  is  studying  should 
now  be  drawn  to  show  a  little  more  than  the  last  year's  growth, 
and  the  following  parts  should  be  pointed  out :  A  terminal  bud, 
an  axillary  bud,  a  supernumerary  bud  (if  present),  a  leaf-scar,  a 
lenticel,  and  one  of  the  ring-like  scale-scars  at  the  base  of  the 
year's  growth. 

II.  STRUCTURE  OF  THE  TERMINAL  BUD. — (1)  Cut  the  twig 
in  two,  transversely,  about  J  cm.  below  the  terminal  bud ;  split 
the  part  bearing  the  latter  from  below  upward,  letting  the  section 
pass  as  nearly  as  possible  through  the  centre  of  the  bud.  If  the 
section  has  been  well  made  with  a  thoroughly  sharpened  knife,  the 
structure  may  now  be  distinctly  seen.  It  will  be  observed  that 
the  bud  consists  of  a  series  of  thin  layers  or  scales,  one  within  the 
other,  and  each  inserted  upon  the  short-conical  prolongation  of  the 
axis  or  stem.  The  scales,  in  fact,  represent  leaves,  and  the  leaves, 
as  is  always  the  case  with  these  organs,  are  borne  upon  a  stem. 
A  bud,  therefore,  is  a  short  stem  with  leaves  very  compactly 
arranged  upon  it. 

(2)  From  one-half  of  the  divided  bud  remove  the  scales  one  by 
one,  beginning  with  the  outer.  It  will  be  seen  that  they  are  not 
all  alike.  The  outer  ones  are  not  so  large  as  those  next  inte- 
rior, and  are  thicker  and  more  woody.  They  are,  moreover, 


STUDY    OF    STEMS.  33 

smooth  or  nearly  so,  while  the  thin  interior  ones  are  densely 
clothed  with  appressed  silky  hairs.  .  These  two  kinds  of  scales 
are  leaves  modified  for  the  protection  of  the  delicate  true  leaves 
which  they  enclose.  When  the  bud  unfolds  in  the  spring,  the 
outer  scales  fall  away  unchanged,  but  the  inner  ones,  especially 
those  next  the  true  leaves,  make  a  feeble  effort  to  become  'foliage : 
they  increase  considerably  in  size  and  acquire  some  greenness  of 
color,  but  soon  fall  away,  yielding  to  the  expanding  foliage  leaves. 
The  more  woody  outer  scales  doubtless  protect  the  true  leaves 
from  mechanical  violence,  such,  for  example,  as  that  due  to  the 
lashing  of  the  branches  during  a  storm  ;  while  the  plush-cov- 
ered inner  ones  protect  them  from  sudden  changes  of  tem- 
perature and  from  the  entrance  of  water.  This  latter  is  accom- 
plished partly  by  the  closeness  with  which  the  scales  are  applied 
to  one  another,  and  partly  by  their  downy  covering,  which  is 
somewhat  oily  and  so  repels  the  water.  If  water  were  permitted 
free  access  to  the  interior,  its  freezing  and  thawing  in  winter 
would,  beyond  question,  harm  or  destroy  the  young  and  delicate 
foliage  leaves  within. 

Examining  now  the  true  leaves,  it  will  be  found  that  there  are 
several  of  these,  small  in  size,  but  with  their  parts  distinctly  rec- 
ognizable under  the  magnify  ing-glass.  They  occur  very  near  to, 
but  just  back  of,  the  stem-apex,  the  youngest  and  smallest  nearest 
of  all.  The  glass  shows  that  these  leaves  are  already  compound, 
thus  contrasting  strongly  with  the  scales,  which  are  simple. 

The  leaflets  are  densely  clothed  with  hairs,  partly  glandular  and 
partly  of  the  ordinary  kind,  both  probably  protective  in  their 
function,  but  the  former,  in  particular,  useful  in  defending  the 
young  and  growing  leaves  from  the  attacks  of  injurious  insects. 

Packed  away  in  small  compass  within  the  bud  is  the  leafy 
branch  of  the  coming  year,  awaiting  only  the  genial  warmth  and. 
moisture  of  spring  to  bring  it  to  its  full  development. 

(3)  Make  a  drawing  of  one-half  of  the  bud,  enlarged  about 
three  diameters,  as  suggested  on  Plate  II.  (Fig.  2),  and  point  out 
one  of  the  outer  bud-scales,  one  of  the  inner  hairy  scales,  one  of 
the  true  leaves,  the  stem-apex,  the  pith,  the  wood,  and  the  bark. 

III.  INTERNAL  STRUCTURE  OF  THE  STEM. — For  this  part  of 
our  study  transverse  and  longitudinal  sections  must  be  made  and 
suitable  reagents  must  be  applied  to  bring  out  the  structure  more 


34  LABORATORY    EXERCISES    IX    BOTANY. 

distinctly.  Make  several  cross-sections,  one  through  the  younger 
portion  of  the  stem,  the  growth  of  last  year,  one  through  a  portion 
two  years  old,  and  a  third  through  a  part  still  older. 

(1)  Without  staining  them,  examine  these  sections  successively 
with  a  magnify  ing-glass.  Each  will  be  seen  to  possess  in  the 
centre  an  angular  pith  surrounded  by  a  layer  of  white  wood,  which 
in  the  first  section  is  rather  thin,  in  the  second  thicker  and  made 
up  of  two  rings  called  rings  of  growth,  and  in  the  third  still 
thicker  and  made  up  of  three  or  more  rings,  one  ring  being  added, 
as  a  rule,  for  each  year's  growth.  It  will  also  be  seen  that  the 
wood  is  crossed  in  a  radial  direction  by  very  numerous  delicate 
lines  which  have  their  origin  in  the  pith  and  terminate  in  the  bark. 
These  are  called  medullary  rays. 

Outside  the  wood  occurs  the  bark,  which  is  also  thinner  in  the 
younger  part  of  the  stem  and  thicker  in  the  older  portions,  though 
this  difference  is  less  marked  than  in  the  case  of  the  wood.  With 
care  the  bark  may,  as  in  the  root  of  Dandelion,  be  distinguished 
into  three  layers :  an  outer,  the  grayish  or  brownish  corky  layer, 
called  the  epiphloeum ;  next  the  latter  a  middle  layer  composed 
chiefly  of  green  cells,  and  hence  called  the  green  layer,  or,  from 
its  position,  the  mesophloeum ;  and  an  inner  layer  or  zone  called 
the  endophloaum,  or  bast-layer,  which  may  be  observed  to  contain 
numerous  masses  of  bast-fibres  distributed  through  softer  tissues. 
The  former  appear  whitish  under  the  magnifying-glass. 

The  delicate  tissue  constituting  a  thin  boundary-zone  between 
wood  and  bark  is  also  called  cambium,  and  here,  as  in  the  Dande- 
lion root,  throughout  the  season  of  growth  new  cells  are  formed 
which  add  to  the  thickness  of  the  wood  on  the  outside  and  to  that 
of  the  bark  on  the  inside. 

(2)  Apply  the  phloroglucin  test.  The  purpose  of  this  test  is  to 
differentiate  the  parts,  so  that  the  structure  may  be  more  easily 
understood.  Apply  to  each  of  the  three  sections  the  test  in  the 
same  manner  as  directed  in  Exercise  I.  The  pith  and  wood  in 
each  case,  it  will  be  observed,  are  stained  red,  though  of  somewhat 
different  shades,  and  in  the  older  portions  of  the  stem,  at  lea-t. 
the  bast-fibres  in  the  inner  layer  of  the  bark  also  stain,  so  that 
they  are  now  more  distinctly  recognizable.  All  the  other  tis-ues 
remain  unstained.  The  bast-fibres  form  wedge-shaped  ma— « •>, 
with  the  thinner  end  of  the  wedire  outward  and  each  ina-s  rn>— ed 


STUDY    OF   STEMS.  35 

both  radially  and  tangentially  by  softer  tissues.  In  the  older 
stems  these  wedges  are  larger,  particularly  longer  in  a  radial 
direction. 

The  staining  of  the  fibres  aids  in  tracing  the  limits  of  the  inner 
bark,  since  the  latter  constitutes  a  zone  bounded  on  the  outside  by 
a  circular  line  joining  the  outer  limits  of  the  bast-wedges.  More- 
over, the  ends  of  the  medullary  rays  which  penetrate  the  bark 
may  now  be  traced  more  easily.  The  coarser  rays  are  made  up 
of  the  soft  tissues  which  separate  laterally  the  bast-wedges  ;  and 
the  finer,  of  those  which  traverse  the  wedges  in  a  radial  direc- 
tion. The  rays  extend  to,  but  do  not  penetrate,  the  middle  bark. 
The  inner  bark  may  therefore  usually  be  distinguished  from  the 
middle  by  its  radial  structure. 

In  many  stems,  though  not  in  the  Hickory,  the  phloroglucin 
test  also  enables  one  to  see  the  medullary  rays  in  the  wood  more 
distinctly. 

(3)  Apply  the  iodine  test.     This  test  is  used  as  directed  in  Exer- 
cise I.,  and  for  the  same  purpose.    It  will  be  observed  that  starch 
occurs  in  the  bark  (particularly  in  the  middle  layer),  in  the  pith 
(especially  in  its  outer  portion),  and  in  the  medullary  rays.     The 
latter  are  therefore  rendered  very  distinct  by  this  test. 

(4)  Apply  the  ferric-chloride  test.     Using  this  test  as  directed  in 
Exercise  I.,  it  will  be  found  that  tannic  matters  occur  more  abun- 
dantly in  the  medullary  rays  than  in  the  wood,  that   the  pith 
contains  but  little  tannin,  and  that  the  bark  contains  it  in  abun- 
dance. 

(5)  Draw  a  diagram  of  the  cross-section  of  the  stem,  selecting 
for  the  purpose  a  part  which  is  at  least  two  years  old.     Let  the 
structure  be  represented  as  magnified  about  five  diameters,  as  in 
PL  II.  Fig.  3.     Point  out  the  epiphloaum,  the  mesophloeum,  the 
endophloeum,  the  cambium  zone,  a  wood  wedge,  a  medullary  ray, 
a  ring  of  growth,  and  the  pith. 

(6)  Study  the  longitudinal  section.     Take  a  fresh  twig,  and  with 
a  sharp  knife  make  a  section  lengthwise  through  the  middle,  pref- 
erably from  the  base  upward,  so  guiding  the  knife  that  one  of  the 
axillary  buds  will  be  bisected.     Apply  to  the  cut  surfaces  such 
tests  as  are  necessary  to  render  the  structure  distinct.     Observe 
that  the  pith  traverses  the  stem  lengthwise  from  end  to  end,  pene- 
trating even  the  axis  of  the  terminal  bud  and  sending  off  branches 


36  LABORATORY    EXERCISES   IN    BOTANY. 

to  the  axillary  ones.  On  either  side  of  the  pith  will  be  seen  a 
white  band  of  wood  ;  adjacent  to  each  of  these  bands,  on  the 
outside,  a  thin  cambium  line  ;  and  next,  a  broader  band  of  bast, 
the  long  fibres  of  which  make  this  layer  of  the  bark  appear  quite 
different  from  the  other  two  layers,  which  may  also  be  traced  as 
thin  longitudinal  bands.  We  can  easily  see,  from  a  comparison 
of  the  transverse  and  longitudinal  sections,  that  the  stem  is  made 
up  of  a  series  of  cylinders :  first,  the  solid  pith ;  then  a  hollow 
cylinder  of  wood  enclosing  it ;  this  in  turn  is  enclosed  by  a  thin 
cylinder  of  cambium,  this  by  a  cylinder  of  bast,  this  by  one  of 
mcsophloeum,  and  the  whole  enveloped  by  a  cylinder  of  epiph- 
keurn  ;  the  tissues  of  these  cylinders,  however,  not  being  dis- 
tinct, but  continuous  from  one  to  the  other,  forming  a  solid  whole. 

Such  is  the  structure  of  the  Hickory  twig ;  and  its  study  has 
given  not  only  a  good  idea  of  Hickory  stems  in  general — for  they 
differ  mainly  in  size  and  in  the  relative  thickness  of  certain  layers 
— but  has  afforded  a  very  good  general  knowledge  of  the  struc- 
ture of  the  stems  of  nearly  all  dicotyls  and  gymnosperms. 

While  the  stems  of  these  plants  differ  in  numerous  structural 
details,  the  general  arrangement  of  tissues  is  the  same  in  all. 
There  is  a  central  pith  surrounded  by  a  cylinder  of  wood  which 
is  crossed  by  medullary  rays ;  •  this  is  enclosed  by  a  cylinder  of 
cambium,  and  this  by  a  three-layered  cylinder  of  bark.  As 
will  be  seen  hereafter,  this  arrangement  is  widely  different  from 
that  found  in  the  stems  of  ferns  and  monocotyls. 

Now  let  the  student,  pursuing  the  same  method,  study,  describe, 
and  figure  twigs  of  one  or  more  of  the  following  plants :  Horse- 
chestnut,  Balsam  Poplar,  White  Ash,  Lilac,  or  any  one  of  the 
other  plants  mentioned  at  the  beginning  of  this  exercise. 


STUDY    OF    STEMS. 


37 


PLATE  II.,  FIG.  1.— Drawing  of  a  Hickory  Twig,  including  about  one  year's  growth 
(%  natural  size) :  cr,  terminal  bud ;  b,  d,  axillary  buds ;  c,  supernumerary  bud ;  e,  leaf- 
scar  ;  /,  scars  of  scales  of  last  year's  terminal  bud. 

FIG.  2.— Drawing  of  Vertical  Section  of  Terminal  Bud  of  Hickory  (magnified  about 
2  diameters) :  a,  one  of  the  inner,  hairy  scales ;  6,  one  of  the  outer,  woody  scales ;  c, 
one  of  the  true  leaves  ;  d,  the  stem-apex ;  e,  the  pith  ;  /,  the  wood  ;  p,  the  bark. 

FIG.  3.— Diagram  of  Cross-section  of  Hickory  Twig,  representing  two  years'  growth 
(magnified  about  3  diameters):  a,  outer  bark  or  epiphlceum;  6,  middle  bark  or  meso- 
phhvum ;  c,  inner  bark  or  endophlceum  ;  d,  wood ;  e,  medullary  ray ;  /,  ring  of  growth  ; 
g,  pith. 


EXERCISE  III. 

STUDY  OF  STEMS:  COMPARISON  OF  TWIGS. 

TWIGS  from  any  of  our  common  trees  or  shrubs,  collected  in 
late  autumn  or  in  early  spring,  will  aiford  very  instructive  studies. 
For  the  purposes  of  this  exercise  the  four  following  are  selected  : 
those  of  the  American  Beech  (Fagus  ferruginea,  Ait.),  those  of 
the  White  Ash  (Fraxinus  Americana,  JL),  those  of  the  Bass  wood 
(Tilia  Americana,  L.\  and  those  of  the  Balsam  Poplar  (Populus 
balsamifera,  L.). 

Directing  attention  first  to  the  Beech  twig,  let  its  peculiarities 
be  noted  and  its  structure  be  compared  with  that  of  the  others. 

I.  EXTERNAL  CHARACTERISTICS. — Note,  first,  that  the  Beech 
twig  is  thin,  cylindrical,  its  grayish  exterior  or  corky  layer  freely 
punctate  with  lenticels  which  are  smaller  than  those  already  ob- 
served in  the  Hickory.  It  is  also  somewhat  zigzag,  being  bent 
at  the  points  where  the  axillary  buds  occur.  At  the  ends  of 
branches  and  in  the  axils  of  leaf-scars  are  observed  also  prom- 
inent scaly  buds,  and  at  intervals  along  the  twigs  or  at  the  bases 
of  the  shorter  branches  compact  clusters  of  ring-like  scale-scars 
marking  the  position  of  the  buds  of  previous  years ;  but  rarely 
if  ever  are  any  adventitious  buds  or  supernumerary  ones  to  be 
found. 

(1)  Phyllotaxy. — But  the  most  conspicuous  differences  between 
the  Beech  twig  and  the  Hickory  twig  are  to  be  found  in  the  form 
and  arrangement  of  the  leaf-scars  and  that  of  the  scales  of  the 
scaly  buds.  Especial  attention,  therefore,  should  be  given  to 
these  points. 

Observe,  first,  that  there  is  only  one  leaf-scar  at  a  node;  and, 
second,  that  the  next  one  higher  up  on  the  stem  is  halfway 
around  from  the  first,  or  on  the  opposite  side,  so  that  there  are 
on  the  stem  two  vertical  rows  of  scars  and  axillary  buds.  Now, 
nearly  all  stems  show  a  great  regularity  in  the  arrangement  of  the 
leaves,  but  this  arrangement  is  by  no  means  the  same  in  different 

39 


40  LABORATORY    EXERCISES    IN    BOTANY. 

plants.  In  the  Hickory  the  arrangement  is  different  from  that  in 
the  Beech,  and  different  still  from  both  in  the  Ash.  In  fact,  two 
different  types  of  arrangement  may  be  distinguished — the  alternate 
and  the  whorled.  In  the  former  only  one  leaf  occurs  at  a  node ; 
in  the  latter  two  or  more ;  but  there  are  many  varieties  of  each 
of  these.  The  Beech  presents  a  very  simple  variety  of  the  for- 
mer, and  the  leaf-arrangement — or  phyttotaxy,  as  it  is  technically 
called — is  expressed  by  the  fraction  one-half.  In  this  fraction  the 
numerator  expresses  the  number  of  turns  about  the  stem  to  com- 
plete a  cycle,  and  the  denominator  the  number  of  leaves  included 
in  the  cycle.  The  fraction  also  expresses  the  angular  distance 
between  successive  leaves,  one-half  the  circumference  of  the  stem, 
or  180°,  intervening  between  one  leaf  and  the  next  in  the  cycle. 
The  denominator  of  the  fraction,  moreover,  expresses  the  number 
of  vertical  rows  of  leaves,  or  orthostachies,  on  the  stem. 

If  the  phyllotaxy  of  the  Beech  be  compared  with  that  of  the 
Hickory  twig,  it  will  be  found  that  the  latter  also  is  alternate ; 
but  the  fraction  which  expresses  it  is  different.  If,  as  in  study- 
ing the  Beech  twig,  the  start  be  made  with  a  leaf-scar  low  down 
on  the  stem,  and  a  line  be  traced  around  it  to  the  next  scar,  and 
so  on  until  the  scar  is  reached  directly  over  the  one  from  winch 
the  start  was  made,  it  will  be  found  that  it  is  the  sixth  leaf  instead 
of  the  third  that  is  directly  over  the  first ;  that  five  scars  have 
been  passed  in  going  from  one  to  the  other,  not  counting  the  last  ; 
and  that  two  circuits  of  the  stem  have  been  made.  The  fraction 
which  expresses  the  phyllotaxy  is  therefore  two-fifths. 

Similarly  examining  other  alternate-leaved  twigs,  it  will  be  found 
that  the  phyllotaxies  -^,  -f,  or  ^  also  exist.  Putting  these  fractions 
together  in  order,  it  will  be  found  that  they  form  a  series,  ^,  -J-,  £, 
-f,  -£$,  etc.,  which  includes  by  far  the  larger  proportion  of  all 
alternate  forms  of  phyllotaxy.  The  members  of  this  series  bear 
a  very  curious  relation  to  each  other.  If  the  numerators  of  the 
first  two  be  added  together  for  a  new  numerator,  and  their  denom- 
inators for  a  new  denominator,  the  third  fraction  in  the  scries  is 
obtained  ;  if  the  second  and  third  be  similarly  treated,  the  fourth 
term  is  obtained  :  and  so  on. 

The  Basswood  twig  agrees  with  the  Beech  in  its  phyllotaxy, 
and  that  of  the  Balsam  Poplar  with  the  Hickory;  but  in  the 
twig  of  the  Ash  there  are  two  leaf-scars  and  two  buds  at  a  node; 


STUDY    OF   STEMS.  41 

this  affords  an  illustration  of  the  other  type  of  phyllotaxy — 
namely,  the  whorled.  It  is  also  the  simplest  form  of  this  arrange- 
ment. It  will  be  observed  that  the  leaves  composing  the  whorl 
are  as  far  apart  as  possible — namely,  opposite  each  other  on  the 
stem,  and  this  variety  of  the  whorled  node  has  hence  been  called 
the  opposite.  It  is  almost  universally  the  case,  whether  the 
leaves  in  the  whorl  be  few  or  many,  that  they  are  placed  at  equal 
distances  apart;  if  two,  180°  apart;  if  three,  120°;  and  so  on. 

It  will  furthermore  be  seen  that  the  successive  whorls  alternate  • 
that  is,  if  a  line  were  drawn  through  the  centre  of  a  pair  of  leaf- 
scars,  this  line  would  cross  at  right  angles  one  drawn  through  the 
centre  of  the  pair  of  scars  next  below  or  of  the  ones  next  above. 
The  whorls,  in  other  words,  are  decussate,  and  this,  too,  is  nearly 
always  true  of  whorled  leaves.  Thus,  in  the  phyllotaxy  where 
the  leaves  are  opposite  or  in  whorls  of  two  there  will  be  four 
vertical  rows  of  leaves  on  the  stem ;  where  they  are  in  whorls  of 
three,  six  rows ;  and,  in  general,  there  are  twice  as  many  vertical 
rows  as  there  are  leaves  in  the  whorl. 

All  this  doubtless  has  reference  to  securing  for  the  leaves  their 
due  proportion  of  light — a  thing  necessary  to  the  proper  perform- 
ance of  their  functions  and  to  the  prevention  of  interference  be- 
tween the  nutritive  currents  that  flow  between  the  leaves  and 
the  stem. 

(2)  Leaf-scars. — Comparing  the  scars  on  the  different  twigs 
studied,  very  considerable  differences  will  be  found  between  them, 
not  only  in  size,  number,  and  arrangement,  but  in  their  shape,  in 
their  markings,  and  in  their  position  as  respects  the  axillary  bud. 
In  the  Beech  they  are  small,  nearly  semicircular  in  outline,  dotted 
with  the  scars  of  several  (about  seven)  leaf-bundles  arranged  in  a 
semicircle,  and  bordered  on  either  side  by  line-like  stipule  scars. 
The  bud  is  not  located  directly  in  the  axil  of  the  leaf-scar,  but 
above  and  somewhat  to  one  side.  Those  of  the  Basswood  are 
similar  in  shape,  but  larger,  the  buds  are  strictly  axillary,  and  the 
bundle-dots  in  the  leaf-scars  are  unequal  in  size  and  usually  about 
six  in  number. 

In  the  Balsam  Poplar  the  scar  is  conspicuous,  few-dotted, 
usually  with  a  broadly  rounded  sinus  above,  into  which  the  bud 
fits,  and  the  lower  end  is  pointed. 

The  leaf-scars  of  the  Ash  are  still  more  prominent,  many-dotted, 


42  LABORATORY    EXERCISES    IX    BOTANY. 

rounded  on  the  sides  and  lower  edge,  and  either  straight  on  the 
upper  margin  or  with  a  shallow  sinus  into  which  the  bud  fits. 

Many  other  interesting  variations  in  the  scars  would  be  found 
if  other  twigs  were  studied  ;  for  example,  those  of  the  Ailanthus, 
the  Sumach,  and  the  Aralia  spinosa  are  enormously  large,  and 
those  of  the  Sycamore  completely  encircle  the  bud,  the  leaf-base 
fitting  over  it  in  the  growing  season  like  a  candle-extinguisher. 

(3)  Bud-scales. — Since  these  are  modified  leaves  or  portions  of 
leaves,  one  would  naturally  expect  to  find  their  phyllotaxy  in 
agreement  with  that  of  the  foliage  leaves  of  the  same  plant. 
This  is,  in  fact,  the  case  in  most  instances,  but  there  are  some 
exceptions,  apparent  or  real.  In  the  Beech,  for  example,  there 
are  four  vertical  rows  of  scales  in  the  bud,  and  but  two  of  ordi- 
nary leaves.  This  deviation  can  be  accounted  for  readily  by  sup- 
posing that  the  scales  represent  the  pairs  of  stipules  at  the  bases 
of  leaves  rather  than  the  leaf-blade;  and  this  is  probably  the  fact. 

In  the  Ash,  the  Basswood,  and  the  Balsam  Poplar,  however,  the 
arrangement  of  the  scales  is  precisely  that  of  the  true  leaves. 

So  many  interesting  peculiarities  do  the  buds  and  leaf-scars  of 
the  branches  of  different  trees  and  shrubs  present  that  it  would 
probably  be  possible,  by  aid  of  them,  to  construct  a  key  for  identi- 
fication of  our  native  species. 

The  student  should  now  make  drawings  and  descriptions  of  an 
equal  number  of  twigs  taken  from  other  trees  or  shrubs. 


STUDY   OF   STEMS, 


43 


PLATE  III.,  FIG.  1.— Twig  of  Beech,  showing,  a,  slender  terminal  scaly  bud;  6,  a 
similar  axillary  bud ;  c,  ring-like  scale-scars  marking  position  of  last  year's  terminal 
bud ;  d,  leaf-scar ;  e,  stipule-scar.  The  small  dots  sprinkled  over  the  stem  represent  the 
lenticels. 

FIG.  2— Twig  of  Basswood,  showing  one-half  phyllotaxy,  like  that  of  Beech. 

FIG.  3.— Twig  of  Balsam  Poplar,  showing  two-fifths  phyllotaxy. 

FIG.  4.— Twig  of  Ash,  showing  opposite  phyllotaxy.    (Each  about  %  natural  size.) 


EXERCISE  IV. 

STUDY  OF  STEMS:   THE  KH1ZOME. 

AMONG  dicotyls  any  of  the  following  plants  will  afford  good 
material  for  study  :  The  Mayapple  (Podophyllum  peltatum,  L.\ 
Culver's-root  (Veronica  Virginica,  Z.),  Cranesbill  (Geranium  mac- 
ulatum,  .L.),-  Blue  Cohosh  (Caulophyllum  thalictroides,  Michx.), 
Peppermint  (Mentha  piperita,  L.)9  and  Yellow  Parilla  (Menisper- 
mum  Canadense,  L.). 

Among  monocotyls  the  following  will  afford  instructive  stud- 
ies :  Solomon's  Seal  (Polygonatum  biflorum,  E?l.9  or  P.  giganteum, 
Dietrich),  Sweet  Flag  (Acorus  Calamus,  L.\  Blue  Flag  (Iris 
versicolor,  L.},  False  Solomon's  Seal  (Smilaciua  racemosa,  Desf.), 
and  Lily-of-the- Valley  (Convallaria  majalis,  L.).  One  rhizome 
from  each  group  will  be  studied  in  this  exercise. 


A. — For  our  first  study  the  rhizome  of  Mayapple  will  be  selected. 
Rhizomes  gathered  in  late  autumn  or  in  early  spring  are  the  most 
suitable  for  the  purpose,  and  the  description  which  follows  applies 
to  such  : 

I.  EXTERNAL  CHARACTERISTICS. — (1)  Removing  the  rhi- 
zome carefully  from  the  soil,  it  will  be  found  that  its  length 
varies  from  two  to  four  feet ;  that  it  grows  horizontally  two  or 
three  inches  beneath  the  surface  of  the  ground;  that,  except 
for  the  swollen  nodes  that  occur  along  it  at  intervals  of  from 
two  to  four  or  five  inches,  it  is  nearly  cylindrical ;  that  from 
these  nodes  it  sends  out  occasional  lateral  branches  similar  to  the 
parent  rhizome ;  and  that  the  posterior  or  older  end  of  the  rhi- 
zome is  in  process  of  decay,  showing  that  increase  in  length  is 
limited,  and  that  as  it  grows  at  the  apex  it  becomes  exhausted 
and  dies  away  at  the  base.  Each  plant  is  thus  year  by  year 
slowly  travelling  through  the  soil ;  moreover,  by  reason  of  the 
lateral  branches  which,  by  this  process,  must  sooner  or  later  be- 


46  LABORATORY   EXERCISES    IN    BOTANY. 

come  detached  from  the  parent  rhizome,  a  large  number  of  new 
plants  must  ultimately  originate. 

It  will  be  observed  further  that  the  rhizome  is  thick  and  fleshy, 
containing  large  stores  of  food-material  to  supply  the  growth  of 
above-ground  parts  when  the  warm  spring  sunshine  stimulates  the 
vital  processes  of  the  plant  to  renewed  activity. 

Examining  carefully  the  brownish  surface,  there  will  be  found 
between  the  more  conspicuous  nodes  angular  scars,  the  scars  of 
scales  that  have  decayed.  These,  since  they  represent  leaves, 
prove  the  rhizome  to  be  a  stem  rather  than  a  root,  because  roots 
never  bear  leaves. 

On  the  upper  sides  of  the  enlarged  nodes  will  be  observed  con- 
spicuous circular  scars,  shown  at  d  on  Plate  IV.  (Fig.  1).  These  are 
either  cup-shaped  or  there  is  a  central  conical  elevation,  in  reality 
a  small  bud.  The  former  are  scars  of  the  above-ground  stems ; 
the  latter,  scars  of  the  large  radical  leaves  of  previous  seasons. 

From  the  sides  and  lower  surfaces  of  the  rhizome,  at  or  near 
the  enlarged  nodes,  arise  numerous  small  roots.  These  differ  in 
origin  from  the  Dandelion  root,  being  outgrowths  from  the  side 
of  the  stem,  and  not  from  its  end.  They  are  therefore  adventi- 
tious, and  not  primary  roots.  The  lateral  roots  borne  by  rhi- 
zomes must,  of  course,  always  be  adventitious. 

Ascending,  or  sometimes  arising  nearly  at  right  angles,  from  the 
end  of  the  rhizome  and  from  the  ends  of  each  of  the  main  branches 
will  be  observed  conspicuous  buds,  which  remind  one,  except  from 
the  texture  of  the  scales,  of  the  terminal  bud  of  the  Hickory. 
These  buds  give  origin  to  an  above-ground  stem  or  leaf,  which, 
when  it  decays  in  autumn,  leaves  a  large  circular  scar,  such  as  has 
already  been  observed  at  the  swollen  nodes.  In  the  mean  time, 
through  the  summer,  the  rhizome  is  pushing  onward  through  the 
soil,  and  at  the  close  of  summer  has  formed  a  new  bud  at  its  apex. 
The  number  of  circular  scars,  therefore,  may  indicate  the  age  of 
the  rhizome. 

(2)  Now  make  a  drawing  of  the  rhizome,  pointing  out  the 
following  parts:  one  of  the  angular  scale-scars;  the  terminal 
bud ;  a  branch  ;  one  of  the  large  circular  scars ;  and  one  of  the 
secondary  roots. 

II.  STRUCTURE  OF  THP:  TERMINAL  BUD. — (l)Cut  the  rhizome 
in  two  a  little  way  hack  from  the  terminal  bud,  and  then  split  it 


STUDY   OF    STEMS.  47 

from  below  upward  through  the  middle.  Some  specimens  will 
show  the  structure  illustrated  on  Plate  IV.  (Fig.  2).  The  scales  are 
much  alike  except  for  size,  and  they  are  not  dry,  like  those  of 
the  Hickory,  nor  are  any  of  them  clothed  with  hairs  or  other- 
wise constructed  with  reference  to  the  exclusion  of  water  or  the 
prevention  of  sudden  changes  of  temperature.  Being  under 
ground,  they  do  not  need  to  be  thus  protected,  the  soil  itself 
serving  the  purpose  perfectly.  Their  main  use  seems  to  be  to 
protect  the  true  leaves  and  stem-apex  from  mechanical  injury  as 
it  grows  onward  through  the  soil. 

Some  of  the  inner  scales,  like  the  corresponding  ones  of  the 
Hickory,  develop  considerably  in  the  spring,  and  often  even  rise 
a  little  above  the  soil ;  but  they  soon  wither  away,  leaving  ring- 
like  scars  on  the  part  of  the  rhizome  which  bore  them.  These 
are  shown  at  e  on  Plate  IV.  (Fig.  1). 

Interior  to  the  scales,  and  enclosed  by  them,  will  be  found  a 
single  well-developed  peltate  leaf  having  its  lobed  blade  plicately 
folded  down  over  the  cylindrical  petiole,  as  shown  in  the  figure. 
These  leaves,  when  mature,  may  reach  to  the  height  of  a  foot,  or 
even  two  feet,  above  the  soil,  and  the  blades  may  attain  the  diam- 
eter of  a  foot. 

The  section  of  the  bud  shows  at  the  base  of  the  petiole  a 
very  minute  bud ;  in  fact,  the  petiole  fits  over  the  latter  like  a 
candle-extinguisher.  When,  in  the  autumn,  the  leaf  falls  away, 
this  bud  appears  as  the  conical  point,  already  alluded  to,  in 
the  centre  of  the  large  circular  scar  that  marks  the  insertion  of 
the  petiole. 

Besides  this  bud,  the  section  shows  still  another,  indicated  at  c 
in  the  figure.  It  usually  occurs,  as  in  the  case  illustrated,  on  the 
under  side  of  the  rhizome  in  the  axil  of  one  of  the  outer  scales 
of  the  terminal  bud.  This  axillary  bud  serves  to  continue  the 
growth  of  the  rhizome  under  ground,  and  the  angular  scars 
already  referred  to  are  the  scars  of  its  scales,  the  latter  being 
carried  apart  by  the  lengthening  of  the  bud-axis,  and  then  with- 
ering away. 

There  may  also  be  other  buds  situated  just  back  of  the  apical 
ones,  giving  rise  to  lateral  offshoots  from  the  rhizome. 

(2)  Make  a  drawing  of  such  a  bud,  magnified  about  two  diam- 
eters, and  point  out  a  bud-scale,  the  petiole  of  the  true  leaf,  the 


48  LABORATORY   EXERCISES   IN   BOTANY. 

bud  that  occurs  at  its  base,  and  the  bud  that  serves  to  continue 
the  growth  of  the  rhizome. 

(3)  Other  terminal  buds  show  a  structure  different  from  that 
described  above.     Instead  of  a  single  large  leaf  in  the  interior, 
will  be  found  a  stern  with  two  opposite  leaves  upon  it  and  termi- 
nated by  a  well-developed  flower-bud,  as  shown  on  Plate  IV.  (Fig. 
3).     This  stem  when  fully  grown  attains  about  the  same  diameter 
and  height  as  the  petiole  of  the  leaf  in  the  former  case,  and  it  has 
much  the  same  appearance,  but  that  it  is  really  a  stem  is  shown 
by  the  fact  that  it  produces  a  flower  and  fruit.     Moreover,  no 
bud  forms  underneath  it,  and  when  it  disappears  in  autumn  it 
leaves  a  cup-shaped  scar,  and  not  one  with  a  conical  elevation  in 
its  centre. 

(4)  Make  a  drawing  of  a  vertical  section  of  one  of  these  buds 
also,  magnified  about  two  diameters,  and  point  out  a  bud-scale, 
the  enclosed  stem,  the  bud  that  serves  to  continue  the  growth  of 
the  rhizome,  a  true  leaf,  and  the  flower-bud. 

III.  THE  INTERNAL  STRUCTURE  OF  THE  RHIZOME. — Podo- 
phyllum  is  a  dicotyl,  though  one  of  altogether  different  habit  from 
that  of  the  Hickory.  Moreover,  the  stem  of  the  Hickory  which 
has  been  studied  was  an  above-ground  one,  while  this  is  an  under- 
ground one.  Great  differences  of  structure  are  therefore  to  be 
expected ;  but  can  the  same  general  plan  or  type  of  structure 
be  traced  in  both  ?  Let  us  see. 

(1)  Making  a  cross-section  and  treating  it  with  the  phloroglucin 
reagent,  about  midway  between  the  circumference  and  the  centre 
of  the  section  will  be  found  a  circle  of  red  dots  from  twelve  to 
twenty  in  number.  These  circles,  though  few  and  small  com- 
pared with  those  of  the  Hickory,  are  the  wood  or  vasal  bundles; 
the  soft  area  enclosed  within  the  circle  constitutes  the  pith ;  and 
the  bauds  of  soft  tissue  which  separate  the  bundles  laterally  from 
each  other  are  the  medullary  rays. 

If  with  the  glass  the  bundles  be  carefully  examined,  each  will 
be  found  to  have  an  inner  part  which  is  stained,  or  partly  so,  by 
the  phloroglucin,  and  an  outer  part  which  is  wholly  unstained, 
yet  distinct  enough  from  the  adjacent  soft  tissues.  The  former  is 
the  wood  or  the  xylem  ;  the  latter,  the  bast  or  phloem  of  the 
bundle.  Extending  in  a  circle  about  the  stem,  between  the  wood 
and  bast,  is  the  cambium ;  the  bast  portions  of  the  bundles,  to- 


STUDY   OF   STEMS.  49 

gether  with  those  portions  of  the  medullary  rays  exterior  to  the 
cambium  zone,  constitute  the  inner  bark ;  the  soft  white  tissues 
still  farther  exterior  make  up  the  middle  bark ;  and  the  exterior 
brownish,  corky  layer  is  the  outer  bark. 

It  is  thus  seen  that  in  all  the  essential  features  of  its  structure 
this  stem  agrees  with  that  of  the  Hickory.  It  clearly  belongs  to 
the  same  type.  In  many  details,  however,  it  differs  from  the 
latter.  For  example,  it  has  but  little  liguified  tissue ;  its  vasal 
bundles  are  shorter,  broader,  and  fewer  ;  there  are  either  no  bast- 
fibres  or  rarely  very  imperfectly  developed  ones ;  the  pith  is  rela- 
tively larger,  is  cylindrical,  and  is  not  composed  of  dead  cells  ;  and 
its  soft  tissues  contain  a  much  greater  abundance  of  starch,  as  re- 
vealed by  the  iodine  test. 

(2)  Make  a  drawing  of  the  cross-section,  magnified  three  or 
four  diameters,  and  point  out  the  following  parts  :  the  outer 
bark ;  the  middle  bark ;  a  bast-bundle  in  the  inner  bark  ;  the 
cambium  zone;  the  wood  of  a  bundle;  and  the  pith. 


B. — The  rhizome  of  a  monocotyl  will  now  be  studied,  that  of  Sol- 
omon's Seal  (Polygonatum  bifloruin)  being  selected  for  the  purpose. 

I.  EXTERNAL  APPEARANCE  AND  CHARACTERISTICS. — (1)  Note 
first  the  more  obvious  resemblances  and  differences  between  this  rhi- 
zome and  that  of  the  Mayapple,  just  studied.  The  former  resembles 
the  latter  in  the  following  particulars :  it  creeps  horizontally  ;  it 
has  numerous  scale-scars  along  its  sides ;  it  has  circular  depressed 
scars  on  its  upper  surface ;  it  has  prominent  nodes  at  the  points 
where  these  scars  occur ;  it  has  a  conspicuous  terminal  bud  ;  it 
sends  off  lateral  shoots ;  it  bears  secondary  roots  on  its  sides  and 
inferior  surface,  especially  on  the  larger  nodes ;  and  it  grows  an- 
nually at  the  apex  while  dying  away  at  the  base. 

The  rhizome  of  Solomon's  Seal  differs  from  that  of  the  May- 
apple  in  the  following  points  :  it  is  more  fleshy  ;  it  is  less  exten- 
sively creeping ;  its  swollen  nodes  are  even  more  swollen,  nearer 
together,  and  flattened  horizontally ;  its  scale-scars  are  more 
crowded  and  less  angular ;  and  the  depressed  scars  on  the  upper 
surface  are  all  of  one  kind,  none  of  them  having  a  bud  in  the 
centre ;  they  are,  in  fact,  all  stem-scars.  There  are  other  minor 
differences,  as  those  of  color,  surface,  length  of  rootlets,  etc. 


50  LABORATORY    EXERCISES    IX   BOTANY. 

So  far,  however,  the  differences  noted  are  only  such  as  might 
occur  between  rhizomes  of  closely-related  plants.  The  student 
must  learn  that  the  most  important  resemblances  and  differences 
are  not  always  the  ones  that  are  the  most  obvious.  In  this 
instance  the  differences  of  greatest  significance  will  be  found  by 
studying  the  internal  structure  of  the  bud  and  the  stem. 

(2)  Now  make  a  drawing  of  the  rhizome  about  natural  size, 
and  point  out  the  following :  one  of  the  cup-shaped  scars  on  the 
upper  side  of  a  swollen  node ;  a  scale-scar ;  a  bud  on  one  of  the 
lateral  branches ;  the  terminal  bud  ;  and  a  root. 

II.  INTERNAL  STRUCTURE  OF  THE  TERMINAL  BUD. — (1)  As 
directed  in  the  former  study,  divide  the  terminal  bud  longitudi- 
nally and  observe  the  internal  structure.     But  little  difference  is 
seen  in  the  texture  and  arrangement  of  the  scales,  but  close  scru- 
tiny of  their  structure  shows  that  the  venation  is  of  the  parallel  or 
nerved  type,  while  in  the  scales  of  the  Mayapple  a  network  is 
distinctly  visible.     This  difference  is  significant,  for  nearly  all 
monocotyls  have  parallel-veined  leaves,  while  nearly  all  dicotyls 
have  reticulate  or  netted  ones. 

In  the  interior  of  the  bud  of  Solomon's  Seal,  as  in  that  of  the 
Mayapple,  is  to  be  found,  packed  away  in  small  compass,  the  shoot 
of  the  coming  season.  In  this  case  the  shoot  consists  of  a  tol- 
erably well-formed  leafy  stem  with  numerous  alternate,  two- 
ranked  leaves  having  minute  flower-buds  already  formed  in  their 
axils.  The  difference  between  the  venation  of  these  true  leaves 
and  those  in  the  bud  of  the  Mayapple  is  still  more  conspicuous 
than  in  the  case  of  the  scales — a  fact  which  will  be  better  under- 
stood when  more  particular  study  is  given  to  leaves. 

Note  that  here  also,  in  the  axils  of  some  of  the  outer  bud- 
scales,  on  the  lower  side  of  the  rhizome,  is  a  minute  bud  whose 
function  it  is  to  continue  the  underground  growth  while  the  above- 
ground  stem  and  its  leaves  and  flowers  are  developing. 

(2)  Make  a  careful  drawing  of  the  bud-section,  magnified  two 
or  three  diameters,  and  point  out  the  following  parts :  a  bud- 
scale;  the  enclosed  stem;  and  the  bud  that  continues  the  growth 
of  the  rhizome. 

III.  INTERNAL  STRUCTURE  OF  THE  RHIZOME. — (1)  Make 
three  different  cross-sections,  preferably  between  the  large  nodes, 
and  treat  one  with  the  phloroglucin  reagent,  another  with  iodine 


STUDY   OF   STEMS.  51 

solution,  and  the  third  with  ferric-chloride  solution.  Neither 
of  these  reagents  gives  very  decided  reactions,  showing  that  the 
structure  possesses  little  if  any  lignified  tissue,  that  starch  is 
either  absent  or  present  only  in  very  minute  quantity,  and  that 
the  same  is  true  of  tannic  matters.  The  case  is  not  unusual. 
Many  stems  show  no  tannin  reactions ;  starch,  though  a  very 
important  food-substance,  is  by  no  means  always  present,  even  in 
organs  which,  like  this,  are  heavily  charged  with  food-materials, 
but  is  replaced  by  some  similar  carbohydrate,  as  iuulin,  sugar,  etc. ; 
and  in  fleshy  organs  such  as  this  lignified  cells  are  seldom  abun- 
dant, and  are  quite  frequently  absent  altogether.  Vasal  or  so- 
called  wood-bundles  are,  however,  present  in  this  rhizome,  as 
they  are  in  that  of  the  Mayapple  and  in  the  stem  of  the  Hickory. 
Their  distribution,  though,  is  wholly  different ;  in  fact,  this  is  one  of 
the  most  characteristic  differences  between  monocotyls  and  dicotyls. 
Examining  closely  the  iodine-treated  section,  there  will  be 
observed,  scattered  without  order  through  the  section,  a  consider- 
able number  of  dots,  distinguishable  from  the  adjacent  tissue  by 
their  somewhat  browner  color.  True,  the  dots  do  not  come  quite 
to  the  periphery  of  the  section,  there  being  a  narrow  zone  next 
the  exterior  where  few  or  none  are  found,  but  within  this  zone 
they  are  numerous  and  scattered  without  apparent  order,  as 
shown  in  the  diagram,  Plate  V.  (Fig.  3).  These  dots  are  the  vasal 
bundles.  The  zone  exterior  to  them — the  blank  area  a  in  the 
figure — is  the  cortex,  forming  a  region  in  the  stem  which  is  anal- 
ogous to  the  middle  bark  and  epidermis  of  the  dicotyl.  The  part 
within,  containing  the  bundles,  is  the  central  cylinder.  Not  infre- 
quently, though  not  in  this  stem,  a  sheath  of  woody  tissue  sepa- 
rates the  one  zone  from  the  other.  This  when  present  is  called 
the  cylinder-sheath.  The  bundles  are  commonly  more  crowded 
next  this  sheath  than  they  are  farther  interior.  As  in  the  May- 
apple,  they  are  bundles  of  stringy  tissues  running  lengthwise  of 
the  stem,  but  they  are  destitute  of  cambium,  and  so,  of  course, 
such  stems  do  not  possess  a  cambium  zone.  These  differences 
apply  in  the  main  to  the  two  great  groups  of  plants  which  they 
represent.  Let  these  differences  be  grasped  firmly :  A  dicotyl 
stem  has  a  three-layered  bark,  separated  from  the  wood  by  a 
cambium  zone ;  the  vasal  bundles  are  arranged  radially  about  a 
central  pith,  and  are  separated  from  each  other  laterally  by 


52  LABORATORY   EXERCISES   IN    BOTANY. 

medullary  rays ;  and  such  a  stem  increases  in  thickness  by 
growth  in  the  cambium  zone,  some  of  the  newly-formed  cells 
adding  to  the  thickness  of  the  wood  on  its  exterior  and  to  the 
inner  bark  on  its  interior.  On  the  other  hand,  a  monocotyl  stem 
has  no  distinct  bark  and  no  cambium  zone ;  its  vasal  bundles  are 
not  arranged  in  a  circle,  but  scattered  through  the  central  cylinder ; 
there  are  no  medullary  rays ;  and,  although  the  centre  of  such  a 
stem  is  usually  softer  than  the  exterior,  there  is  no  proper  pith. 

The  two  groups  may  therefore  nearly  always  be  distinguished 
by  merely  inspecting  cross-sections  of  their  stems,  and  it  makes 
little  difference  whether  the  stems  selected  for  the  purpose  be 
above-ground  or  subterranean  ones. 

This  general  rule,  however,  has  a  few  exceptions.  A  curious 
instance  in  point  is  the  above-ground  stem  of  the  Mayapple. 
The  bundles  which  form  a  circle  in  the  rhizome  send  off  numer- 
ous branches  which,  rising  into  the  above-ground  stem,  become 
scattered  irregularly  through  it,  instead  of  preserving  their  radial 
arrangement,  so  that  this  stem  closely  resembles  in  structure  a 
monocotyl. 

In  a  few  other  plants  the  stems  exhibit  a  structure  somewhat 
intermediate  between  the  two  types,  possessing  characteristics 
of  both. 

(2)  Make  a  diagram  of  the  cross-section  of  the  stem  of  Solo- 
mon's Seal,  magnified  three  or  four  diameters,  and  point  out  the 
following :  the  cortex  ;  the  boundary  between  cortex  and  central 
cylinder ;  a  rootlet,  if  present ;  and  one  of  the  vasal  bundles. 

The  cross-section  of  the  root  of  the  same  plant  shows  a  struc- 
ture quite  different  from  that  of  the  stem.  Instead  of  many 
scattered  small  bundles,  it  has  a  single  large  central  one,  which 
shows  a  radial  structure  of  its  elements,  and  is  surrounded  by  a 
sheath,  as  shown  on  Plate  V.  (Fig.  4).  a  is  a  root-hair ;  6,  the  cortex ; 
c,  the  bundle.  These  differences  are  usual  between  the  stems  and 
the  roots  of  monocotyls,  so  that,  by  examining  the  structure  of  a 
small  fragment,  the  root  may  easily  be  distinguished  from  the 
stem.  These  differences  will  be  considered  more  fully  hereafter, 
when  the  study  of  the  microscopic  structure  of  roots  and  stems 
is  reached. 

Now  study,  describe,  and  illustrate  one  of  the  other  monocotyl 
rhizomes  mentioned  at  the  beginning-  of  this  exercise. 


STUDY   OF   STEMS. 


53 


STUDY   OF   STEMS. 


55 


PLATE  V.,  FIG.  1.— Drawing  of  Rhizome  of  Polygonatum  biflorum  (about  %  natural 
size) :  a,  cup-shaped  stem-scar  on  upper  surface  of  enlarged  node  ;  b,  scale-scar ;  c,  bud 
on  lateral  branch  ;  d,  terminal  bud  ;  e,  adventitious  root. 

FIG.  2.— Drawing  of  Vertical  Section  of  Terminal  Bud  (enlarged  about  1^  diameters) : 
a,  bud-scale ;  6,  young  stem  within  the  bud,  bearing  undeveloped  leaves  and  flower- 
buds  ;  c,  bud  serving  to  continue  underground  growth  of  rhizome. 

FIG.  3.— Diagram  of  Cross-section  of  Rhizome  (enlarged  about  2  diameters) :  a,  cortex  ; 
6,  boundary  between  cortex  and  central  cylinder;  c,  rootlet;  d,  one  of  the  vasal  bundles. 

FIG.  4.— Diagram  of  Cross-section  of  Root  (magnified  about  7  diameters):  a,  root-hair; 
6,  cortex;  c,  central  radial  bundle  enclosed  in  the  bundle-sheath. 


EXERCISE  V. 

STUDY  OF  STEMS:   THE  TUBER. 

THE  following  plants  afford  good  studies  :  The  Potato  (Solan um 
tuberosum,  L.\  the  Jerusalem  Artichoke  (Helianthus  tuberosus, 
Z.),  the  Indian  Cucumber- root  (Medeola  Virginiaua,  JL),  the 
Toothwort  (Dentaria  laciuiata,  Muhl\  the  Spring  Beauty  (Clay- 
tonia  Virginica,  L.\  the  Ground-nut  (Apios  tuberosa,  Moench.), 
the  Monkshood  (Aconitum  Napellus,  Z.),  the  Madeira  Vine 
(Boussingaultia  baselloides),  and  the  Crosnes  (Stachys  tuberifera, 
Naudin). 

The  most  easily  procurable  of  these,  as  well  as  one  of  the  best 
for  the  purpose,  is  the  Potato.  If,  before  the  potatoes  are  ripe 
in  the  autumn,  one  of  the  plants  be  dug  up  carefully,  break- 
ing the  underground  parts  as  little  as  possible,  it  will  be  observed 
that  the  tubers  are  borne  at  the  ends  of  slender  underground 
branches  which  are  sent  out  in  abundance  from  the  subterranean 
portions  of  the  true  stem.  Examining  these  branches  with  care, 
scales  will  be  discovered  upon  them.  They  are  therefore  also 
stems — in  fact,  rhizomes — such  as  we  have  already  studied,  and 
the  tubers  they  bear  at  the  ends  are  really  only  excessively  thick- 
ened portions  of  this  rhizome.  A  tuber,  therefore,  is  only  a 
stem  still  further  modified  and  disguised,  and  on  giving  it  close 
inspection  it  will  be  found  that,  despite  its  distorted  form,  it  pos- 
sesses all  the  essential  characteristics  of  an  ordinary  stem. 

I.  EXTERNAL  CHARACTERISTICS. — (1)  Axillary  Suds. — The 
tuber  has  these  buds,  the  same  as  an  ordinary  stem.  This  is 
the  nature  of  the  so-called  "  eyes."  Examining  one  of  these 
with  care,  there  will  be  found  in  the  bottom  of  each  depression 
one  or  more — usually  several — very  imperfectly  developed  buds, 
destined,  when  growth  takes  place,  to  form  the  "  sprouts "  or 
true  stems.  The  largest  one  of  the  cluster  is  the  axillary  bud, 
and  the  others,  arranged  about  it,  are  supernumerary.  Many 
a  boy  who  has  had  to  "  sprout "  potatoes  in  his  father's  cellar 

57 


58  LABORATORY    EXERCISES    IX    BOTANY. 

has  learned  that  after  the  first  set  of  sprouts  have  been  removed 
others  spring  from  near  the  same  place,  so  that  the  tedious  ope- 
ration may  have  to  be  repeated.  The  first  set  of  sprouts  are  from 
axillary,  the  others  from  supernumerary,  buds. 

(2)  Leaf-scars. — Just  below  this  cluster  of  buds  may  be  seen 
a  transversely  elongated  scar  with  a  minute  scaly  point  at  its  mid- 
dle.    This  point,  rudimentary  as  it  is,  really  represents  a  leaf. 
It  is  a  leaf  which  has  wholly  lost  its  functions  and  is  on  the 
verge  of  disappearance  altogether.     This  is  a  good  illustration  of 
a  not  uncommon  fact  in  the  organic  world.     There  are  few  of  the 
higher  plants  or  animals  that  do  not  show  in  some  portion  of  their 
structure  a  rudimentary  organ  wholly  useless  or  perhaps  even  more 
or  less  injurious  to  its  possessor,  yet  highly  significant  to  the  stu- 
dent as  showing  the  relationships  of  the  organism  or  indicating 
the  course  of  its  descent  from  pre-existing  organisms.     So  in  this 
case  these   leaf-scars  show   unmistakably  that  the   organ  which 
bears  them  is  a  stem,  and  not  a  root,  and  that  this  stem  was  prob- 
ably modified  or  specialized  from  one  of  the  ordinary  forms,  thus 
suiting  it  to  new  functions.     What  these  functions  are  is  evident 
from  the  study  of  the  habits  of  the  plant.     The  above-ground 
parts,  and  even  the  roots,  perish  in  the  autumn,  but  the  tubers, 
each  stored  with  abundant  nutriment,  persist  and  give  rise  to  a 
multitude  of  new  plants  the  succeeding  year.     The  tubers  are 
stems  specially  adapted  to  the  propagation  of  the  species. 

(3)  Terminal  Bud. — But  there  are  other  resemblances  between 
this  and  an  ordinary  stem  which  must  not  be  passed  by.     It  has 
a  lower  or  basal  end,  and  an  upper  or  apical  one.    At  the  former 
will  be  found  the  scar  of  its  attachment  to  the  thin  rhizome  on 
which  it  was  borne.    At  the  qpposite  end  will  be  noted  a  terminal 
bud,  as  in  other  stems.     This  bud  does  not  differ  essentially  in 
structure  from  the  axillary  ones,  save  that  it  is  not  subtended  by 
a  scale,  and  is  apt  to  be  stronger  than  they,  and  therefore  to  be 
capable  of  a  more  vigorous  growth.     Partly  because  of  this  fact, 
and   partly  because  the  axillary  buds  are   more   numerous  and 
stronger  toward  this  than  toward  the  basal  end,  this  end  of  the 
potato  is  often  called  the  "seed  end." 

The  greater  development  and  the  crowded  character  of  the  buds 
toward  the  apex  are  other  points  of  resemblance  between  this  tuber 
and  most  ordinary  stems. 


STUDY   OF   STEMS.  59 

(4)  Phyllotaxy. — Here,  again,  stem-characters  are  clearly  shown, 
but  to  study  the  phyllotaxy  successfully  it  is  necessary  that  a 
tuber  should  be  selected  which  is  not  too  distorted  and  irregular 
in  its  growth.  Having  made  the  proper  selection,  inspection  will 
disclose  the  fact  that  the  "  eyes  "  appear  in  spirals,  as  shown  on  Plate 
VI.  (Fig.  1),  where,  to  render  the  fact  still  more  evident,  they  are 
connected  by  dotted  lines.  This  renders  it  certain  that  the  arrange- 
ment is  orderly  and  definite,  though  by  the  usual  method  it  might 
be  somewhat  difficult  to  determine  the  precise  phyllotaxy.  This 
can,  however,  easily  be  ascertained  by  the  aid  of  the  spiral  lines 
shown.  Several  sets  of  spirals  might  be  traced,  some  running 
nearly  horizontal,  others  nearly  perpendicular,  and  some  passing 
from  right  to  left,  others  from  left  to  right.  For  this  purpose 
there  must  be  selected  two  sets,  one  including  those  spirals  nearest 
the  perpendicular  which  pass  from  left  to  right,  and  the  other  in- 
cluding those  nearest  the  perpendicular  which  pass  from  right  to 
left.  Counting  the  number  of  spirals  in  each  direction,  it  will 
usually  be  found  that  there  are  three  of  one  and  five  of  the  other. 
The  smaller  number,  three,  gives  the  numerator  of  the  fraction 
expressing  the  phyllotaxy,  and  the  sum  of  the  two  numbers, 
iight,  gives  the  denominator.  The  phyllotaxy  is  therefore  three- 
eighths.  The  same  method  is  applicable  to  other  short  stems  on 
rhich  the  leaves  or  scales  are  much  crowded — as,  for  example,  to 
e  cones  of  the  pines  and  firs. 

II.  INTERNAL  STRUCTURE. — (1)  Arrangement  of  Tissues. — 
llaking  a  cross-section  through  the  tuber  in  such  a  manner  that 
it  will  pass  through  one  of  the  axillary  buds,  the  following  facts 
ill  be  observed  : 

First,  a  rather  distinct  circle  of  dots  (as  shown  at  c,  PL  VI.  Fig.  2) 
considerable  distance  within  the  margin  of  the  section,  except 
'here  the  bud  occurs  ;  here,  however,  the  circle  approaches  the 
largiu  and  passes  into  the  bud.     Each  one  of  these  dots  really 
'presents  the  outer  end  of  a  wood  wedge,  each  homologous  with 
the  ones  observed  in  the  Hickory  twig,  but  here  possessing  but 
little  lignified  matter.       Immediately  outside  this  circle  is  the 
imbium  zone. 

Secondly,  there  will  be  observed,  interior  to  this,  scattered  dots 
rhich  are  really  fragments  of  the  inner  portions  of  the  same  bun- 
lies.  These  dots,  it  will  be  noted,  do  not  occur  all  through  the 


60  LABORATORY    EXERCISES   IN    BOTANY. 

interior,  but  there  is  an  area  of  greater  or  less  size  that  is  free 
from  them — the  pith  (/,  PI.  VI.  Fig.  2),  and  from  this  outward  may 
be  traced  many  curved  and  more  or  less  irregular  branches  which 
separate  the  bundles  above  referred  to.  These  are  the  medullary 
rays.  One  of  them  is  shown  at  k  on  Plate  VI. 

Thirdly,  in  the  bark — that  is,  in  the  region  outside  the  cam- 
bium zone  above  referred  to,  and  about  midway  between  it  and 
the  outside — will  be  found  another  circle  of  dots,  fainter  than  the 
first,  shown  at  d  on  Plate  VI.  These  dots  constitute  the  outer 
portion  of  the  bast,  and  their  outer  limit  marks  that  of  the  inner 
layer  of  the  bark,  or  endophloeum.  From  this  to  the  brownish 
exterior  layer  is  the  mesophlo3um,  and  the  exterior  brownish, 
corky  layer  is  the  exophloeum. 

It  will  thus  be  seen  that  in  its  essential  features  the  internal 
structure  of  this  stem  agrees  with  that  of  other  stems,  and  par- 
ticularly with  that  of  the  Hickory  and  other  dicotyl  plants.  It 
is,  in  fact,  modified  from  the  type  only  so  much  as  is  necessitated 
by  its  very  succulent  habit. 

(2)  Tests. — Applying  the  phloroglucin  test,  there  will  be  found, 
as  might  be  expected,  very  little  lignified  tissue.  There  are  faint 
indications  of  it  in  the  row  of  dots  at  c,  and,  if  these  could  be 
examined  with  the  compound  microscope,  it  would  be  found  that 
the  cells  which  show  this  reaction  are  ducts — large  tubes  formed 
of  coalesced  cells  found  in  wood. 

The  iodine  test  shows  great  abundance  of  starch.  It  is  this 
substance  which  gives  to  the  tuber  its  chief  value  and  causes  it  to 
be  so  extensively  employed  for  food.  It  is  this  also  which  nour- 
ishes the  buds  and  enables  them  to  develop  into  new  plants  when 
the  tuber  is  planted.  The  starch-grains  of  the  potato  are  unusu- 
ally large,  and  can  readily  be  seen  with  a  magnify  ing-glass,  appear- 
ing as  glistening  white  particles. 

If  the  test  be  applied  with  care,  it  will  readily  be  seen  that  the 
starch  is  not  quite  equally  distributed  through  the  tuber.  It  is  a 
little  less  abundant  next  the  corky  outside  than  it  is  farther  inte- 
rior. Here,  in  fact,  albuminous  matters  are  abundant,  while 
starch  is  small  in  quantity.  The  reverse  is  the  case  with  the 
interior  cells.  These  facts  are  worthy  of  consideration  in  the 
preparation  of  the  potato  for  food. 

Applying  the  ferric-chloride  test,  it  will  be  found  that  :i  faint 


STUDY   OF   STEMS. 


61 


green  color  is  produced  in  the  section,  showing  that  tannic  mat- 
ters are  present.  This  accounts  for  the  tarnishing  of  a  bright  knife- 
blade  when  used  for  paring  the  tubers,  the  tannin  acting  upon 
the  iron  to  produce  tanuate  of  iron. 

Another  fact  worthy  of  note  in  connection  with  the  potato  tuber 
is  that,  when  exposed  for  some  time  to  strong  light,  it  becomes 
green.  This  is  due  to  the  development  of  chlorophyll  in  the 
cells  of  the  mesophlceum  ;  but  accompanying  this  change  is  the 
development  of  a  poisonous  principle  which  communicates  an 
acrid  taste  to  the  tuber  even  when  cooked.  Cattle,  in  fact,  have 
been  poisoned  by  feeding  upon  potatoes  which  have  turned  green 
by  exposure. 

The  above-ground  green  parts  of  the  potato  plant  contain  poi- 
sonous matter  also,  and  it  is  worth  remembering  that  the  family  to 
which  the  plant  belongs — the  Solanacese — contains  many  of  the 
most  dangerous  of  the  vegetable  poisons,  as  belladonna,  stra- 
monium, and  hyoscyamus. 

The  student  should  now  make  a  parallel  study  of  one  or  more 
of  the  other  tubers  mentioned  at  the  beginning  of  this  exercise. 


STUDY   OF   STEMS. 


63 


PLATE  VI.,  FIG.  1.— Tuber  of  Solanum  tuberosum  (%  natural  size),  showing,  a,  termi- 
nal bud ;  6,  axillary  bud  ;  c,  one  of  the  scales  subtending  an  axillary  bud ;  d,  scar  where 
tuber  was  attached  to  underground  shoot. 

FIG.  2.— Transverse  Section  of  Tuber  (%  natural  size) :  a,  one  of  the  axillary  buds ; 
6,  a  supernumerary  bud ;  c,  one  of  the  circle  of  dots,  the  outer  part  of  the  xylem  of  one 
of  the  bundles;  d,  one  of  the  circle  of  dots,  the  outer  part  of  the  bast  or  phloem  of  a 
bundle ;  e,  cambium ;  /,  pith  ;  g,  mesophloeum ;  h,  endophlceum ;  i,  exophloeum ;  A,,  one 
•of  the  medullary  rays. 


EXERCISE  VI. 

STUDY  OF  STEMS:  THE  CORM. 

THE  following  afford  good  examples  for  study:  Gladiolus 
(G.  cornmunis,  Z.,  or  G.  psittacinus),  Crocus  (C.  vernus,  Willd., 
or  C.  sativus,  L.)9  Colchicum  (C.  autumnale,  L.\  Indian  Turnip 
(Arissema  triphyllum,  Torr.),  Green  Dragon  (Arisjema  Dracou- 
tium,  Schott),  Calladium  (C.  esculentum). 

The  first  in  this  list  is  selected,  as  the  corms  are  easily  procur- 
able and  are  very  typical  in  their  structure.  Here,  as  in  the  rhi- 
zome, is  to  be  found  a  stem  in  disguise,  only  it  is  disguised  still 
more  effectively.  It  is,  in  fact,  a  broad,  thick,  erect  rhizome 
covered  with  thin  dry  scales. 

I.  EXTERNAL  CHARACTERISTICS. — (1)  The  Scales  and  Buds. 
—Remove  these  scales  one  by  one,  observing  their  structure  and 
mode  of  insertion.  They  are  brown  and  veiny,  with  the  veins 
parallel  below  and  becoming  somewhat  netted  toward  the  top, 
where  they  are  also  shreddy ;  they  are  inserted  one  above  the 
other  on  the  corm,  and  not  on  one  side  only,  but  all  the  way 
around ;  when  they  are  removed  they  show  a  succession  of  cir- 
cular scars  one  above  the  other.  Just  above  each  scar  will  usu- 
ally be  seen  a  bud,  and  these  buds  appear  in  alternate  order,  form- 
ing two  ranks,  showing  that  the  scales  really  have  the  one-half 
arrangement,  as  is  the  fact  with  the  true  leaves  of  the  same  plant 
and  of  other  plants  of  the  same  family,  the  Iridacese. 

It  will  be  observed  that,  as  in  many  ordinary  stems,  the  lower 
axillary  buds  are  minute  and  very  imperfectly  developed,  those 
higher  up  being  successively  larger,  and  the  terminal  bud  being 
largest  of  all.  During  the  growing  season  the  lateral  buds  may 
give  rise  to  new  corms — another  means,  besides  the  seeds,  of  mul- 
tiplying the  plants. 

(2)  The  Stem. — Aside  from  the  buds,  what  is  left,  after  remov- 
ing the  scales,  is  the  main  stem,  a  thick  fleshy  mass  which  bears 
little  semblance  to  an  ordinary  stem,  but  which  certainly  is  one, 


65 


66  LABORATORY    EXERCISES   IN   BOTANY. 

because  it  bears  leaf-scales  and  axillary  buds.  Its  surface  is 
punctate  with  numerous  depressed  points,  and  is  also  distinctly 
furrowed  longitudinally.  The  lower  or  rooting  end  is  deeply 
depressed,  and  the  terminal  bud  arises  from  a  similar  deep  de- 
pression in  its  upper  or  apical  end.  Aside  from  these  depres- 
sions, however,  the  corm  is  usually  nearly  twice  as  broad  as 
high.  The  lower  end  gives  rise  to  numerous  nearly  simple 
adventitious  roots. 

If  now  the  corm  be  cut  transversely  into  two  nearly  equal  por- 
tions, two  regions  are  clearly  distinguishable  :  a  central  cylinder 
region,  in  which  there  are  numerous  scattered  vasal  bundles,  and 
which  is  more  or  less  angular  in  its  outline,  and  a  thick  cortical 
region  which  exudes  a  copious  yellow  milk-juice  and  which  is 
crossed  by  occasional  bundles.  Toward  its  periphery  also  it  is 
dotted  with  cells  containing  red  or  other  coloring-matter. 

The  few  scattered  bundles  found  in  the  cortex  are  those  which 
pass  out  from  the  central  cylinder  to  supply  the  leaves  and  buds. 
Aside  from  this  unusual  thickness  of  the  cortex,  the  stem-struc- 
ture is  clearly  like  that  of  other  monocotyls  which  have  been 
studied. 

(3)  Tests. — Applying  the  phloroglucin  test,  there  will  be  found, 
as  in  other  succulent  stems,  but  little  lignified  tissue,  and  that  con- 
fined to  the  vasal  bundles. 

Applying  the  iodine  test,  abundance  of  starch  will  be  found. 
The  parenchyma  cells,  particularly  those  of  the  cortex,  are,  in 
fact,  well  filled  with  it. 

The  ferric-chloride  test  also  reveals  the  presence  of  taunic  mat- 
ters, both  in  the  outer  cortex  and  in  the  vicinity  of  the  cylinder- 
sheath,  and  also  within  the  latter. 

Let,  now,  one  or  more  of  the  other  corms  mentioned  at  the  be- 
ginning of  this  exercise  be  studied  and  described  by  the  student. 


STUDY   OF   STEMS. 


67 


PLATE  VII.,  FIG.  1.— Conn  of  Gladiolus  (about  %  natural  size),  deprived  of  its  outer 
covering  of  scales  :  a,  terminal  bud ;  b,  axillary  bud  ;  c,  scar  of  one  of  the  scales  ;  d,  one 
of  the  longitudinal  furrows ;  e,  adventitious  root. 

FIG.  2.— Transverse  Section  of  same  Corm :  a,  outer  cortex  dotted  with  cells  contain- 
ing coloring  matter ;  b,  one  of  the  vasal  bundles  on  its  way  through  the  cortex  from  the 
central  cylinder  to  supply  a  scale  ;  c,  cylinder-sheath ;  d,  one  of  the  vasal  bundles  in  the 
central  cylinder. 


EXERCISE  VII. 

STUDY  OF  STEMS:  THE  BULB. 

FKOM  the  following  list  selections  for  study  may  be  made :  (1) 
Scaly  bulbs :  The  White  Lily  (Lilium  candidnm,  L.\  the  White 
Japan  Lily  (Lilium  Japonicum,  Willd.\  the  Tiger  Lily  (Lilium 
tigrinum,  Ker.\  the  Wild  Orange-red  Lily  (Lilium  Philadelphi- 
cum,  X.),  the  Wild  Yellow  or  Canada  Lily  (Lilium  Canadense, 
L.)y  the  Violet  Wood-sorrel  (Oxalis  violacea,  L.).  (2)  Tunicated 
bulbs :  The  St.  James  Lily  (Amaryllis  formosissima,  Willd.),  the 
Atamasco  Lily  (Amaryllis  Atamasco,  L.\  the  Onion  (Allium 
Cepa,  L.\  the  Garlic  (Allium  sativum,  jL),  the  Wild  Onion  (Al- 
lium cernuum,  Roth.\  the  Wild  Hyacinth  (Camassia  Frazeri,  Torr.\ 
the  Common  Hyacinth  (Hyacinthus  orientalis,  L.),  the  Adder's 
Tongue  (Erythronium  Americanum,  Ker.\  the  Daffodil  (Nar- 
cissus Pseudonarcissus,  L.\  and  the  Snowdrop  (Galanthus  niv- 
alis,  L.). 

The  study  may  be  divided  into  two  parts,  the  scaly  bulb  being 
first  taken  up,  and  afterward  the  tunicated  one. 

I.  THE  SCALY  BULB  OF  LILIUM  CANDIDUM. — This  bulb  is 
easily  procurable  and  is  typical  of  its  kind. 

(1)  How  it  Differs  from  a  Corm. — Like  the   latter,  and   like 
the  tuber  and  rhizome,  it  is  an  underground  stem.     In  shape  it 
also  much  resembles  the  corm,  and,  like  it,  is  surcharged  with 
nutritious  matters.     But  a  very  obvious  difference  is  the  fact  that 
in  this  the  scales  are  succulent  and  heavily  charged  with  nutritious 
matters,  while  in  the  corm  they  are  thin  and  scarious,  the  nutri- 
ment being  almost  wholly  stored  in  the  fleshy  axis. 

(2)  Nature  of  the  Scales. — These  fleshy  scales  bear  even  less 
resemblance  to  ordinary  leaves  than  do  corm-  or  bud-scales,  and 
yet  it  is  obvious  that  they  must  be  regarded  as  modified  leaves,  for, 
in  the  first  place,  they  have  the  same  orderly  arrangement,  and 
their  phyllotaxy  might  even  be  determined  in  the  same  way  as 
was  done  in  the  case  of  the  potato  ;  and,  in  the  second  place,  they, 

69 


70  LABORATORY    EXERCISES   IN    BOTANY. 

occasionally  at  least,  bear  buds  in  their  axils  in  the  same  manner 
as  do  ordinary  leaves.  Still  further  evidence,  if  any  were  needed, 
could  be  found  by  tracing  the  gradations  between  the  outer  or 
lower  scales  and  the  inner  or  upper  ones.  The  latter  develop 
into  true  leaves,  while  the  former  do  not,  and  yet  they  grade 
insensibly  one  into  the  other. 

(3)  Likeness  of  a  Bulb  to  a  Bud. — A  bud  has  been  defined  as 
a  very  short  axis  on  which  imperfectly-developed  leaves  are  com- 
pactly arranged.     If  a  longitudinal  section  through  the  lily-bulb 
be  made,  it  will  be  seen  how  closely  this  definition  applies  to  the 
bulb.     Buds  may,  in  fact,  under  certain  conditions  become  bulbs. 
For  example,  the  Tiger  Lily  of  the  gardens  bears  axillary  buds 
which  are  precisely  similar  to  ordinary  axillary  buds  except  that 
the  scales  in  development  become  fleshy,  and  after  a  time  the  buds 
separate  from  the  plant  and  fall  to  the  ground.     Each  one  of 
these,  when  planted  in  the  soil,  becomes  a  bulb  essentially  like 
the  one  being  studied.     Such  fleshy  buds,  or  bulbils,  as  they  are 
technically  called,  are  also  produced  by  other  plants,  notably  by 
different  species  of  the  genus  Allium,  and  they  are  efficient  means 
of  propagating  the  species. 

(4)  The  Roots. — The  bulb-axis  shows  its  resemblance  to  other 
stems  not  only  in  the  fact  that  it  bears  leaves,  but  also  in  the  fact 
that  it  bears  roots.     In  this  instance  the  roots  are  of  the  fibrous 
variety  and  numerous,  and  it  may  easily  be  seen  that  they  arise 
laterally  from  the  stem  and  are  not  downward  continuations  of 
it.     In  fact,  they  may  often  be  found  originating  above  some  of 
the  lower  scale-scars.     They  are  therefore  adventitious  roots. 

(5)  Venation  of  Scales. — Studying  carefully  the  surface  of  the 
scales,  and  examining  cross-sections  of  them,  it  will  easily  be  deter- 
mined that  the  venation  is  parallel,  or  the  kind  that  usually  occurs 
in  monocotyl  plants,  the  group  to  which  the  Lily  belongs. 

(6)  Making  a  cross-section  of  the  stem,  there  will  also  be  observed 
the  same  scattered  arrangement  of  the  vasal  bundles  that  belongs 
to  the  stems  of  monocotyls. 

II.  THE  TUNICATED  BULB  OF  AMARYLLIS  FORMOSISSIMA. — 
This  might  at  first  be  taken  for  a  corm,  to  which  it  bears  a  greater 
external  resemblance  than  it  does  to  the  Lily  bulb.  This  mis- 
take will  be  corrected,  however,  when  a  longitudinal  section  of  the 
bulb  is  made  and  its  structure  is  studied.  It  will  now  be  found 


STUDY   OF   STEMS. 


71 


that,  as  in  the  Lily  bulb,  the  great  bulk  is  composed  of  fleshy 
scales,  and  these  are  also  inserted  on  a  short,  inconspicuous  axis. 

(1)  Why  called  Tunicated. — The  most  conspicuous  difference  is 
in  the  arrangement  of  the  scales.     Each  is  a  leaf  whose  attach- 
ment to  the  stem  extends  all  the  way  around,  and  each  leaf  in 
succession  encloses  and  conceals  from  view  all  those  interior  to  it 
or  inserted  higher  up  on  the  axis.     They  form  thus  a  succession 
of  coats,  one  within  the  other ;  hence  a  bulb  of  this  kind  is  called 
a  coated  or  tunicated  bulb,  to  distinguish  it  from  one  like  that  of 
the  Lily,  which  is  termed  scaly, 

(2)  Kinds  of  Scales. — Another  difference   is   observed.      The 
exterior  dark-brown  or  blackish  scales  are  dry  or  scarious,  and 
serve  purely  a  protective  purpose,  while  the  interior  colorless  ones 
are  used,  like  those  of  the  Lily,  as  storehouses  for  food. 

In  the  Amaryllis  also,  even  more  easily  than  in  the  Lily,  can 
be  traced  the  relations  between  the  scales  and  ordinary  leaves. 
Many  of  the  interior  scales  may,  indeed,  be  traced  directly  upward 
into  true  leaves.  They  are,  in  fact,  leaf-bases. 

The  scales  are  all  distinctly  parallel-veined,  and  the  stem  shows 
the  characteristic  structure  of  monocotyl  stems. 


STUDY   OP   STEMS. 


73 


PLATE  VIII.,  FIG.  1.— Drawing  (%  natural  size)  of  bulb  of  Lilium  candidum :  a,  one 
of  the  bulb-scales  ;  b,  lower  or  exposed  part  of  the  stem  or  axis ;  c,  an  adventitious  root. 

FIG.  2.— Longitudinal  Section  of  the  Bulb  of  Lilium  candidum  (]A  natural  size) :  a,  one 
of  the  succulent  scales;  b,  one  of  the  imperfectly  developed  true  leaves;  c,  imperfectly 
formed  stem,  destined  to  rise  above  ground  and  to  bear  leaves  and  flowers ;  d,  bulb-axis ; 
€,  axillary  bud  ;  /,  adventitious  root. 

FIG.  3.— Bulb  of  Amaryllis  formosissimum  (%  natural  size) :  a,  section  of  leaves  con- 
centrically arranged  ;  6,  frayed  upper  margin  of  one  of  the  scales ;  c,  one  of  the  exterior, 
dry  scales ;  d,  an  adventitious  root. 

FIG.  4.— Longitudinal  Section  of  the  same :  a,  one  of  the  outer,  dry  scales ;  6,  section 
of  one  of  the  axillary  buds  ;  c,  section  of  another  axillary  bud  ;  d,  the  bulb-axis,  show- 
ing numerous  scattered  fibro-bundles ;  c,  an  adventitious  root. 


FORM  FOR  STUDY  OF  STEMS. 


I.  KIND. 

14.  Floccose. 

13.  Prickling. 

1.  Aerial. 

15.  Hispid. 

14.  Saline. 

(1)  Caulis. 

16.  Strigose. 

15.  Alkaline. 

(2)  Caudex. 

17.  Spinose. 

16.  Acidulous. 

(3)  Culm. 

« 

18.  Echinate. 

(4)  Scape. 

19.  Aculeate. 

XI.  ODOR. 

(5)  Tendril. 

20.  Annulate. 

1.  Odorless. 

(6)  Runner. 

21.  Channelled. 

2.  Faint. 

(7)  Sucker. 

22.  Fissured. 

3.  Agreeable. 

(8)  Offset. 

Transversely. 

4.  Aromatic. 

(9)  Stolon. 

Longitudinally. 

5.  Fragrant. 

(10)  Thorn. 

6.  Mint-like. 

(11)  Cladophyll. 

V.  TEXTURE. 

7.  Balsamic. 

2.  Stibterrancan. 

1.  Succulent. 

8.  Camphoraceous. 

(1)  Rhizome. 

2.  Woody. 

9.  Terebinthinate. 

Slender. 

10.  Pungent. 

Fleshy.. 

VI.  DURATION. 

11.  Musky. 

(2)  Tuber. 

1.  Herbaceous. 

12.  Disagreeable. 

(3)  Conn. 

Annual. 

13.  Irritating. 

(4)  Bulb. 

Biennial. 

14.  Nauseous. 

Scaly. 

Perennial. 

15.  Narcotic. 

Tunicated. 

2.  Suffruticose. 

16.  Fetid. 

HriTT-  .  T^,-, 

3.  Fruticose. 

17.  Putrid. 

.   OHAPE. 

4.  Arborescent. 

• 

1.  Terete. 

5.  Arboreous. 

XII.  INTERNAL  STRUCTURE. 

2.  Flattened. 

3.  Alate. 
4.  Triquetrous. 
5.  Quadrangular. 
6.  Pentangular. 
7.  Fluted. 

VII.  FRACTURE. 
1.  Short. 
2.  Brittle. 
3.  Splintery. 

1  .  Fern  type. 
(1)  Cortex, 
a.  Thickness  compare 
with  that  of  cer 
tral  cylinder. 

8.  Solid. 

4.  Fibrous. 

6.  Bundles  in  : 

9.  Hollow. 

5.  Horny. 

Numerous. 

10.  Irregular. 
11.  Jointed. 

6.  Corky. 
7.  Mealy. 
8.  Friable. 

Few. 

Lignified. 
Unlignified. 

III.  DIRECTION  AND  HABIT. 

c.Sclerenchyma-fibres 

1.  Erect. 

VIII.  CLEAVAGE. 

(2)  Central  cylinder. 

2.  Ascending. 

1.  Regular. 

a.  Bundles  in  : 

3.  Reclinate. 

2.  Irregular. 

Numerous. 

4.  Decumbent. 

3.  Difficult. 

Few. 

5.  Procumbent. 

4.  Easy. 

All  in  one  circle. 

6.  Repent. 

In  more  than  on< 

7.  Voluble. 

IX.  COLOR. 

circle. 

8.  Scaudent. 

1.  Exterior. 

One    circle   witl 

IV.  SURFACE. 

2.  Interior. 

extra     bundle 

1.  Glabrous. 
2.  Glaucous. 
3.  Glandular. 
4.  Rugose. 

5.  Scabrous. 

X.  TASTE. 

1.  Insipid. 
2.  Bland. 
3.  Sweet. 
4.  Bitter. 

in  centre. 
Lignified. 
Unlignified. 
(3)    Masses   of   lignified 
tissues  not  a  part 
of  the  bundles. 

6.  Verrucose. 
7.  Pubescent. 
8.  Puberulent. 

5.  Mucilaginous. 
6.  Pungent. 
7.  Acrid. 

(4)  Starch, 
a.  Most   abundant    in 
cortex 

9.  Sericeous. 
10.  Lanuginous. 
11.  Tomentose. 

8.  Warm. 
9.  Cooling. 
10.  Astringent. 

b.  Most    abundant    in 
central  cylinder. 
(5)  Tannic  matters. 

12.  Villose. 

11.  Nauseous. 

o.  Most   abundant    in 

13.  Pilose. 

12.  Burning. 

cortex. 

FORM  FOR  STUDY   OF  STEMS  (CONTINUED). 


6.  Most    abundant    in 

(2)  Bark. 

Broad. 

central  cylinder. 

a.  Thickness  relative  to 

Lignified. 

2.  Monocotyl  type. 

wood. 

Unlignified. 

(1)  Cylinder-sheath. 

b.  Layers. 

e.  Xylem  wedges. 

a.  Distinct. 

Indistinct. 

Narrow. 

b.  Indistinct. 

Distinct. 

Medium. 

c.  Lignified. 

Relative    thickness 

Broad. 

d.  Unlignified. 

of— 

Lignified. 

(2)  Cortex. 

Exophloeum. 

Unlignified. 

a.  Thickness  compared 

Mesophloeum. 

/.  Ducts. 

with    central    cyl- 

Endopbloeum. 

Conspicuous. 

inder. 

c.  Mesophlceum. 

Inconspicuous. 

6.  Bundles  in  : 

Stone-cells. 

Numerous. 

Numerous. 

Numerous. 

Few. 

Few. 

Few. 

g.  Fissuring. 

Lignified. 

d.  Endophlo3um. 

Fissured. 

Unlignified. 

Distinctly  radiate. 

Unfissured  or  entire 

(3)  Central  cylinder. 

Indistinctly  radiate. 

h.  Pith. 

a.  Bundles  in  : 

Not  radiate. 

Large. 

Numerous. 

Bast-masses. 

Small. 

Few. 

Stratified. 

Entire. 

Lignified. 

Unstratified. 

Hollow. 

Unlignified. 

Shape. 

(4)  Starch. 

b.  Solid. 

Conical. 

a.  Most  abundant  in  — 

c.  Hollow. 

Linear. 

Mesophloeum. 

(4)  Starch. 

Oblique. 

Endophlceum. 

a.  Most    abundant    in 

Curved. 

Medullary  rays. 

cortex. 

Bast-fibres. 

Xylem  wedges. 

b.  Most    abundant    in 

Numerous. 

Pith. 

central  cylinder. 

Few. 

b.  No  starch. 

(5)  Tannic  matters. 

Strongly  /  ligni- 

(5)  Tannic  matters. 

a.  Most    abundant   in 

Slightly    1  fied. 

a.  Most  abundant  in— 

cortex. 

Unlignified. 

Exophloeum. 

b.  Most    abundant    in 

(3)  Woody  cylinder. 

Mesophlceum. 

central  cylinder. 

a.  Distinctly  radiate. 

Endophlceum. 

3.  Dicotyl  type. 

b.  Indistinctly  radiate. 

Cambium  zone. 

(1)  Cambium  zone. 

c.  Annulate. 

Medullary  rays. 

a.  Distinct. 

d.  Medullary  rays. 

Xylem  wedges. 

&.  Indistinct. 

Narrow. 

Pith. 

Medium. 

6.  No  tannic  matters. 

EXERCISE  VIII. 

STUDY  OF  A  LEAF. 


THE  student  has  already  studied  leaves  in  the  form  of  bud-, 
bulb-,  and  corm-scales,  and  has  thus  learned  that  they  may  assume 
various  disguises.  There  is,  in  fact,  no  other  organ  of  the  plant 
that  passes  through  so  many  modifications.  Leaves  may  be  found 
changed  to  spines  for  defensive  purposes,  as  in  the  Barberry  and 
Cactus ;  or  in  the  form  of  tendrils  to  serve  the  plant  for  climb- 
ing, as  in  the  Pea  and  Vetch ;  or  modified  into  insect-traps  of  various 
kinds,  as  in  Dioncea,  Sarracenia,  and  Utricularia ;  or  changed  into 
the  various  organs  of  the  flower  to  subserve  the  function  of  repro- 
duction. The  leaf  will  hereafter  be  studied  in  several  of  these 
disguises,  but  for  the  present  will  be  considered  in  its  more  typical 
form,  that  of  a  foliage  leaf. 

Even  this  assumes  a  great  many  different  shapes  and  forms  on 
different  plants,  and  sometimes  even  several  different  ones  on  the 
same  plant ;  but  it  is  usually  a  flattened,  bilaterally  symmetrical 
organ,  having  distinct  upper  and  under  surfaces. 

Leaves,  of  whatever  sort,  are  outgrowths  from  a  stem.  They 
always  occur  in  regular  order  upon  it,  nearly  always  accord- 
ing to  some  form  of  the  alternate  or  of  the  whorled  plan,  and  in 
acropetal  succession  ;  that  is,  the  oldest  leaf  is  always  the  lowest 
down  on  the  stem,  the  youngest  highest  up  or  nearest  the  apex, 
every  leaf  beginning  its  growth  just  back  of  the  stem-apex. 

Foliage  leaves  are  pre-eminently  the  digestive  organs  of  the 
plant.  The  food  is  partly  brought  to  them  through  the  stem,  and 
partly  taken  up  by  the  leaves  themselves  directly  from  the  atmo- 
sphere. They  also  always  possess  the  green  coloring-matter  called 
chlorophyll,  although  in  a  few  instances  this  is  more  or  less  ob- 
scured by  the  presence  of  other  coloring-matters ;  and  this  green 
matter  is  essential  to  the  digestive  process.  By  aid  of  the  sun- 
light chlorophyll  is  able  to  bring  into  combination  the  elements  of 
the  relatively  simple  mineral  substances  carbon  dioxide  and  water, 

75 


76  LABORATORY    EXERCISES    IX    BOTANY. 

and  to  make  of  them  a  complex  organic  substance,  a  carbohydrate, 
which  in  turn  is  employed  by  the  living  matter  of  the  plant  in 
building  up  the  tissues,  in  enlarging  the  roots,  the  stems,  and  the 
leaves  themselves,  and  in  producing  flowers  and  fruit. 

The  leaf,  then,  is  an  organ  which,  by  aid  of  light,  elaborates 
the  plant's  food.  It  is  a  mechanism  which  makes  use  of  the 
force  which  resides  in  the  sun's  rays  to  do  the  constructive  work 
of  the  plant.  Leaves,  consequently,  are  usually  so  constructed 
and  arranged  upon  the  stem  as  to  secure  as  full  exposure  to  the 
light  as  possible.  In  studying  their  forms  and  phyllotaxy  it  is 
important  to  bear  this  fact  in  mind.  It  will  help  to  explain 
many  things. 

For  this  first  study  of  leaves  those  of  any  of  the  following 
plants  may  be  selected :  the  Horseshoe  Geranium  (Pelargonium 
zonale,  Wittd..),  the  Quince  (Cydonia  vulgaris,  Persoon),  the  Apple 
(Pyrus  Malus,  Z.),  the  Bird  Cherry  (Primus  avium,  Z.),  the 
Black  Cherry  (Primus  serotina,  Ehrh.),  the  Crab-apple  (Pyrus 
corouaria,  Z.),  the  Hawthorn  (Crataegus  coccinea,  Z.),  the  Marsh- 
mallow  (AHbcea  officinalis,  Z.),  the  Hollyhock  (Althaea  rosea, 
Cat;.),  the  Hibiscus  (Hibiscus  Syriacus,  Z.),  the  Basswood  (Tilia 
Americana,  Z.),  and  the  Tulip  Tree  (Liriodendron  tulipifera,  Z.). 

Selecting  for  the  present  purpose  the  first  named  in  this  list,  the 
student  will  observe — 

(1)  The  Parts. — Here  are  present  all  the  parts  which  any  leaf 
can  possess — namely,  an  expanded  portion,  the  lamina  or  blade ; 
a  stalk-like  portion  by  which  the  lamina  is  attached  to  the  stem, 
called  the  petiole  ;  and,  at  the  base  of  this  latter,  two  small  flat- 
tened bodies,  one  on  either  side,  called  the  stipules.     Let  these 
parts  be  studied  in  succession. 

(2)  The  Lamina. — This  consists  of  different  parts,  the  first  to 
be  noted  being  a  framework  or  system  of  veins  branching  out 
from  the  top  of  the  petiole  and  forming  a  complicated  network 
through  the  lamina.     Holding  the  leaf  up  to  the  light,  it  will  be 
<>!».-( Tved  that  these  veins,  though  thicker  than  the  intermediate 
portions  of  the  leaf,  are  more  transparent;  they,  in  fact,  contain 
relatively  little  chlorophyll.     Their  function  is  partly  to  form  a 
support  for  the  rest  of  the  leaf,  partly  to  distribute  to  it  nutritive 
matters  from  tin-  stnn  ;  and    how  admirably  it  is   fitted   for  both 
purposes !     Secondly  will  be  noted  the  deep-green  filling  between 


STUDY  OF  A   LEAF.  77 

the  veins,  the  most  important  part  so  far  as  the  digestive  function 
is  concerned.  This  part  is  called  the  mesophyll.  Lastly,  it  will 
be  observed  that  the  whole  is  covered,  above  and  below,  by  an 
epidermis  which  is  protective  in  its  function,  preventing  the  too 

ipid  evaporation  of  the  leaf-juices  and  guarding  the  delicate 
interior  tissues  from  the  depredations  of  insects,  fungi,  etc. 
Though  thin,  its  cells  are  tough-walled,  compactly  arranged, 

id  partially  cutinized,  the   cutin  (another  name  for  cork-sub- 

tance)  rendering  it  highly  impermeable  to  moisture,  and  so  pre- 
senting excessive  evaporation. 
In  this  case  also  the  epidermis  is  provided  with  numerous  hairs, 

>me  of  the  ordinary  kind,  and  others  glandular,  which  afford  a 

:ill  further  protection  against  insects. 

If  a  piece  of  the  epidermis  be  stripped  off  and  held  up  to  the 
light,  it  will  be  found  colorless  and  transparent.  The  greenness 
)f  the  leaf  is  therefore  not  at  all  due  to  the  epidermis,  but  to  the 

ilorophyll  particles  in  the  sub-lying  cells. 

'3)  The  Two  Surfaces. — Comparing  these,  it  will  be  seen  that 
they  are  by  no  means  alike.  First,  they  differ  in  depth  of  color, 
upper  being  of  a  darker  green  than  the  lower  surface.  This 
due  to  the  fact  that  the  chlorophyll-bearing  cells  of  the  meso- 
)hyll  are  more  compactly  arranged  and  contain  more  chlorophyll- 
lies  next  the  upper  surface  than  next  the  lower ;  and  this  is 
learly  always  the  case  with  those  leaves  whose  two  surfaces  are 
lot  .equally  exposed  to  the  light.  Secondly,  the  veins  stand  out 
)rominently  on  the  lower  or  dorsal  surface,  but  are  less  prominent, 
>r  even  depressed,  on  the  upper  or  ventral  surface.  This  also  is 

ie  fact,  with  most  leaves,  and  it  enables  us  in  most  cases  readily 
distinguish  between  the  dorsal  and  ventral  surfaces  even  when 

ie  leaves  are  detached  from  the  plant.  Thirdly,  a  close  inspection 
)f  the  two  surfaces  under  the  magnifying-glass  shows  that  the  dor- 
sal surface  is  more  abundantly  provided  with  hairs,  and  that  these 
are  longer,  particularly  on  the  veins.  This  also  is  usually  the  case 
where  leaves  possess  hairs  at  all.  In  some  instances  there  are  none 
at  all  on  the  ventral  surface,  while  the  dorsal  surface  may  be  densely 
clothed  with  them.  This  is  probably  because  the  latter  is  more  in 
need  of  protection.  If  the  two  surfaces  could  be  examined  with 
a  compound  microscope,  the  lower  surface  would  be  found  to  pos- 
sess numerous  stomata,  or  breathing  apertures — little  doors,  so  to 


78  LABORATORY    EXERCISES   IN    BOTANY. 

speak,  which  the  plant  may  open  to  get  rid  of  superfluous  moist- 
ure, or  close  to  prevent  its  too  rapid  escape.  These,  except  in 
leaves  that  expose  the  two  surfaces  equally  to  the  light,  are  much 
the  more  abundant  on  the  dorsal  surface,  and  are  frequently  ab- 
sent altogether  from  the  ventral  surface.  The  former  is  therefore, 
unless  specially  protected,  the  more  vulnerable  to  insects  and  ger- 
minating fungus-spores. 

In  this  leaf  also  the  upper  surface  is  marked  with  a  peculiar 
brown  horseshoe-shaped  band,  which  has  given  origin  to  the  pop- 
ular name  of  the  plant,  Horseshoe  Geranium.  This  band  is  due 
to  the  presence  of  a  brownish  coloring-matter  dissolved  in  the  sap 
of  those  mesophyll  cells  lying  adjacent  to  the  upper  epidermis,  but 
its  use  is  unknown. 

(4)  Shape  of  the  Lamina. — It   is   important  that  leaf-forms 
should  be  described  with  precision.    First,  we  distinguish  the  base, 
or  the  end  which  is  attached  to  the  petiole  or  stem  ;  then  the  ajx'.r, 
or  the  end  opposite  the  base ;  and  then  the  margin,  or  the  edges 
between  the  base  and  the  apex. 

In  describing  the  blade  it  is  best  first  to  describe  the  general 
outline;  that  is,  the  outline  without  regard  to  the  particular  form 
of  the  base,  apex,  or  margin.  In  this  view  the  leaf  is  round  or  or- 
bicular. Next  describe  the  base.  It  is  deeply  and  sharply  cleft — 
a  fact  which  is  described  by  the  word  cordate,  or  heart-shaped. 
Next  describe  the  apex,  which  in  this  instance  is  blunt  or  obtuse. 
Lastly,  describe  the  margin,  which  is  doubly  scalloped  ;  that  is, 
there  is  a  set  of  large  scallops,  and  these  again  are  divided  into 
smaller  ones.  A  scallop-margined  leaf  would  be  described  as 
crenate  ;  this  leaf,  being  doubly  scalloped,  is  described  as  bit-mmfc. 

(5)  Surface  of  the  Lamina. — This,  as  has  been  seen,  is  hairy, 
and,  since  the  hairs  are  soft,  short,  and  some  of  them  glandular, 
the  surface  is  described  as  glandular-pubescent.     The  leaves  of 
different  plants  differ  widely  in  this  respect.     Some  are  glabrous, 
or  smooth;  some  glaucous,  or  covered  with  an  easily  removable 
powder;  some  are  scabrous,  or  rough  and  harsh  to  the  touch; 
some  are  lanuginous,  or  covered  with  woolly  hairs;  some  arc 
spinose,  or  covered  with  spiny  hairs  or  prickles ;  and  so  on. 

(6)  Tin-  /o-////r  of  the  lamina  should  also  be  observed  and  de- 
scribed.    Some  leaves,  as  has  been  seen,  are  not  green,  but  of 

other  color,  and  dry,  such  as  bud-scales,  the  scales  of  conns, 


STUDY   OF   A   LEAF.  79 

and  many  stipules.  Such  leaves  are  called  scarious,  while  ordi- 
nary green  ones  are  herbaceous.  Either  may  be  membranous 
(thin  and  pliable),  coriaceous  (of  the  texture  of  leather),  or  succu- 
lent (thickened  but  soft),  but  it  is  not  often  that  any  but  scarious 
leaves  are  hard  and  woody  in  their  texture ;  this,  however,  is 
sometimes  the  case  with  the  leaves  of  tropical  evergreens.  The 
one  now  being  studied  is  herbaceous  and  membranous. 

[The  student  should,  as  soon  as  possible,  become  familiar  with 
the  terms  employed  in  leaf-description  by  studying  the  chapter  on 
"  The  Leaf "  in  College  Botany  or  in  the  Elements  of  Botany. ~\ 

(7)  The  Petiole. — This  in  the  Geranium  is  long  and  cylindrical, 
or  nearly  so,  though,  if  examined  closely,  it  will  be  found  to  be  dis- 
tinctly channelled  on  its  upper  surface  near  its  base  or  junction  with 
the  stem.    It  is  seldom  the  case  that  any  petiole  is  wholly  destitute 
of  this  channel,  or,  at  least,  of  some  flattening  on  its  upper  sur- 
face, and  very  commonly  the  flattening  or  channelling  extends  its 
whole  length.     We  may  therefore  by  this  means  also  tell  the  dor- 
sal from  the  ventral  surface  of  the  leaf.     The  petiole  has  also  a 
distinct  enlargement  at  its  base  or  junction  with  the  stem,  called 
the  pulvinus. 

The  petiole  of  Geranium  is,  like  the  blade,  covered  with  a 
glandular  pubescence. 

The  petiole  may  undergo  a  variety  of  modifications.  It  may  be 
flattened  vertically  or  horizontally ;  it  may  even  become  thin  and 
blade-like,  taking  the  place  of  the  blade  functionally  while  the 
latter  organ  disappears  ;  or  it  may  itself  be  altogether  wanting,  in 
which  case,  the  blade  being  inserted  directly  upon  the  stem,  the 
leaf  is  described  as  sessile. 

(8)  The  Stipules. — These  two  bodies  are  much  like  small  blades 
in  texture  and  appearance.     They  have  a  framework  of  veins,  a 
green  mesophyll,  and  a  glandular-pubescent  epidermis.      They 
probably  perform  to  some  extent  the  functions  of  blades,  Helping 
to  digest  the  plant- food;  but  this  function  in  the  Geranium  is  but 
temporary,  for  in  the  older  leaves  we  find  them  withered  and 
scarious.     Their  chief  use,  perhaps,  is  to  protect  the  remainder  of 
the  leaf  while  in  the  bud.    Indeed,  it  very  often  happens  that  this 
is  their  only  function,  since  in  many  plants  they  fall  away  as  soon 
as  the  buds  unfold. 

In  some  plants  the  stipules  are  attached  by  their  base  to  the 


80  LABORATORY    EXERCISES    IN    BOTANY. 

base  of  the  petiole;  in  others  they  are  partly  attached  to  the 
petiole  and  partly  to  the  stem ;  in  others  still  they  are  partly  or 
wholly  adnate  to  the  sides  of  the  petiole,  and  not  infrequently  are 
so  blended  with  it  as  to  have  lost  their  identity,  forming  a  sheath- 
ing base  to  the  petiole  which  partially  or  wholly  clasps  the  stem ; 
and,  lastly,  in  a  few  plants  the  two  stipules  not  only  grow  fast  to 
the  petiole  by  one  edge,  but  adhere  to  each  other  by  the  other  edge, 
forming  a  sheath  or  ochrea  about  the  stem.  They  are  also  some- 
times modified  into  thorns  or  tendrils  or  honey-glands,  and  in  many 
plants  are  wanting  altogether. 


STUDY   OF   A   LEAF. 


81 


PLATE  IX.,  FIG.  l.—Leaf  of  Pelargonium  zonale  (%  natural  size) :  a,  cordate  base;  6, 
bicrenate  margin ;  c,  dark-colored  zone  on  upper  surface ;  d,  obtuse  apex  of  blade ;  e, 
petiole ;  /,  pulvirius,  or  enlarged  base  of  petiole;  g,  one  of  the  stipules. 

FIG.  2.— A  Stipule  separated  (about  natural  size). 

FIG.  3  —Somewhat  magnified  Cross-section  of  Petiole  through  Pulvinus :  a,  channelled 
upper  surface ;  b,  one  of  the  vasal  bundles ;  c,  convex  lower  surface. 


EXERCISE   IX. 

STUDY  OF  PKEFOLIATION. 

THE  following  plants  afford  variety  and  interest  from  this' 
standpoint :  the  Beech  (Fagus  ferrugiuea,  Ait.),  the  Tnlip  Tree 
(Liriodendron  tulipifera,  L.),  the  Azalea  (Rhododendron  arbor- 
escens,  Torr.),  the  Cherry  (Primus  avium,  L.),  the  Clover  (Tri- 
folium  prateuse,  L.),  the  Violet  (Viola  palmata,  L.,  var.  cucul- 
lata,  Gray),  the  Shield  Fern  (Aspidium  acrostichoides,  Swartz.), 
the  Royal  Fern  (Osmunda  regalis,  L.),  the  Yellow  Dock  (Rumex 
crispus,  L.),  the  Bine  Flag  (Iris  versicolor,  L.),  the  Water-Lily 
(Nuphar  adveua,  Ait.). 

The  term  "  prefoliatiou  "  has  reference  to  the  arrangement  of 
leaves  in  the  bud ;  not  to  their  phyllotaxy,  which  has  already 
been  explained,  but  to  the  coiling,  folding,  or  overlapping  of  the 
leaves. 

Prefoliatiou  may  be  considered  in  two  aspects :  first,  with  ref- 
erence to  the  individual  leaf — how  it  is  bent,  folded,  rolled,  etc. ; 
or  with  reference  to  the  relative  arrangement  of  the  leaves  com- 
posing a  whorl  or  cycle — whether  they  overlap  or  not,  and,  if 
they  do,  what  is  the  manner  of  the  overlapping.  The  subject  is 
best  studied  in  early  spring  when  the  buds  begin  to  unfold. 

For  the  first  study  let  the  bud  of  the  Beech  be  selected. 

(1)  Prefoliation  of  Beech. — The  mature  leaf  is  illustrated  on 
Plate  X.  (Fig.  1),  and  the  young  leaf,  just  issued  from  the  bud,  but 
not  yet  fully  unfolded,  is  shown  on  Plate  X.  (Fig.  2).  In  the  latter 
the  scarious  and  deciduous  stipules  are  seen  still  attached  to  the 
base.  They  have  served  their  purpose  as  bud-scales,  and  are  now 
about  to  disappear.  A  careful  inspection  of  this  young  leaf-blade 
shows  that  the  two  sides  have  each  been  thrown  into  numerous 
regular  parallel  folds,  one  for  each  rib  of  the  leaf,  and  these  folds 
have  been  pressed  closely  upward  against  the  midrib — a  mode  of 
pre foliation  which  is  appropriately  called  plicate.  By  this  arrange- 
ment the  young  leaf  is  made  to  occupy  a  relatively  small  space  in 

83 


84  LABORATORY    EXERCISES    IX    BOTANY. 

the  bud,  and  even  this  space  is  still  further  diminished  by  an  in- 
ward curvature  of  the  edges  which  renders  the  inner  or  ventral  sur- 
iiu  v  MHiu'what  trough-shaped.  The  leaf  is  therefore  also  somewhat 
involute.  Into  this  concavity  fits  closely  the  convex  side  of  the 
next  higher  and  somewhat  smaller  leaf  in  the  cycle,  and  so  on. 

An  examination  of  the  arrangement  discloses  the  fact  that 
Nature  has  done  a  wonderfully  skilful  piece  of  packing  in  the 
construction  of  the  bud.  The  study  also  enables  one  to  account 
for  the  gracefully  elongated  form  of  the  buds. 

But  Nature  does  not  always  accomplish  her  results  by  the  same 
methods.  There  is  an  endless  variety  both  in  methods  and  results. 
A  different  but  scarcely  less  interesting  prefoliation  is  seen  in  the 
Clover. 

(2)  Prefoliation  of  Clover. — Figure  3  (PI.  X.)  represents  a  branch 
of  Trifolium  pratense  with  two  leaves  fully  developed,  and 
another  just  emerging  from  the  bud,  and  not  yefc  unfolded.  It 
will  be  observed  that  each  leaf  consists  of  a  ternately  compound 
blade,  a  long  petiole,  and  a  pair  of  adnate  stipules.  These  last, 
as  is  true  of  most  stipules,  play  an  important  part  in  the  pre- 
foliatiou. 

Examining  now  the  blade  of  the  youngest  of  the  three  leaves 
in  the  figure,  it  will  be  perceived  that  each  leaflet  is  folded  length- 
wise on  its  midrib  in  such  a  manner  that  the  ventral  surface  is 
interior  and  that  the  three  leaflets  are  pressed  close  together  side 
by  side.  The  arrangement  will  easily  be  understood  by  reference 
to  Plate  X.  (Fig.  4),  which  shows  the  same  leaf  removed  from  the 
plant  and  having  its  leaflets  slightly  separated  from  each  other. 

Before  their  emergence  from  the  bud  their  relative  arrangement 
and  folding  were  the  same,  but  the  blade  was  much  smaller  and 
wholly  enclosed  by  the  two  stipules  of  the  leaf  immediately 
below.  In  fact,  on  Plate  X.  (Fig.  4)  the  stipules  (a)  are  wrapped 
about  and  conceal  a  still  younger  leaf,  which  is  folded  as  already 
described,  but  whose  edges  face  in  the  opposite  direction.  This 
i-  called  the  conduplicate  mode  of  prefoliation,  and,  although 
quite  different  from  the  last,  serves  the  purpose  of  compactness 
equally  well.  A  third  and  quite  different  mode  still  is  that 
illustrated  in  the  Yellow  Dock. 

(.".)  1  ^'foliation  of  Yellow  Dock— Figure  5  (PL  X.)  also  shows 
a  branch  with  tw<»  nearly  mature  leaves  and  one,  younger,  not  yet 


STUDY   OF    PREFOLIATION.  85 

unfolded.  The  leaves  here  consist  of  a  long  lanceolate  blade  hav- 
ing a  toothed  and  crispate  margin,  a  strongly-developed  petiole 
which  is  flat  on  its  upper  surface  and  convex  below,  and  stipules 
which  have  coalesced  to  form  a  membranous  ochrea  which  con- 
tinues to  enclose  the  younger  leaves  even  until  the  latter  have 
attained  a  length  of -an  inch  or  more,  when  the  ochrea  ruptures 
and  scales  off.  Each  of  these  young  leaves  is  rolled  from  its 
two  margins  in  such  a  manner  that  the  dorsal  or  lower  surface 
is  interior.  This  mode  of  prefoliatiou  is  called  the  revolute. 

Figure  6  (PL  X.)  represents  two  of  the  young  leaves  as  they 
appear  in  transverse  section,  slightly  separated  from  each  other 
and  partly  unrolled.  As  a  matter  of  fact,  in  the  bud  the  leaves 
are  very  closely  rolled,  and  the  flattened  upper  surface  of  the 
rolled  leaf  lies  close  against  the  flat  upper  side  of  the  petiole  of 
the  next  older  leaf. 

The  student  by  studying  the  other  plants  mentioned  at  the 
beginning  of  this  exercise  will  get  a  good  idea  of  all  the  princi- 
pal modes  of  prefoliation,  though  there  are  endless  variations  in 
detail  in  different  plants. 


STUDY    OF    PREFOLIATION, 


87 


PLATE  X.,  FIG.  1.— Leaf  of  Fagus  ferruginea  (^  natural  size). 

FIG.  2.— Young  Leaf  (about  %  natural  size),  showing,  a,  plicate  blade;  &,  one  of  the 
thin,  scarious  stipules:  c,  the  petiole. 

FIG.  3. — Branch  of  Trifoiium  pratense  (%  natural  size),  showing  two  leaves  nearly 
mature,  and  a  young  and  still  folded  leaf,  b,  just  emerged  from  between  the  stipules  of 
the  leaf  a. 

FIG.  4.— The  Young  Leaf  in  Figure  3  removed,  and  its  leaflets  somewhat  separated  from 
each  other,  showing  the  conduplicate  prefoliation.  The  adnate  stipules  overlap  at  their 
edges,  o,  and  enclose  a  still  younger  leaf,  similarly  folded,  but  much  smaller. 

FIG.  5. — Branch  of  Rumex  crispus,  showing  two  nearly  mature  leaves,  and  a  still 
folded  younger  one  that  has  partly  emerged  from  its  stipular  enclosure  :  a,  young  leaf; 
b,  stipular  sheath  or  ochrea  of  next  older  leaf. 

FIG.  6. — Cross-sections  of  two  very  young  Leaves  of  Rumex,  somewhat  unrolled  and 
separated  to  show  the  mode  of  vernation  (magnified  about  2  diameters) :  a,  dorsal  surface 
of  midrib  of  the  older  of  the  two  leaves. 


EXERCISE  X. 
TYPES  OF  LEAF- VENATION. 

A  SELECTION  for  study  may  be  made  from — (a)  The  leaves  of 
almost  any  species  of  Jungermannia,  or  Moss ;  as,  for  example, 
Juugermannia  Schraderi,  Martins;  J.  barbata,  Schreb. ;  Jubula 
Hutchinsise,  Dumoi't. ;  Funaria  hygrometrica,  Sibth.  •  Bryum 
roseum,  Schreb. ;  Minium  serratum,  Laich.  (b)  Leaves  of  the 
following  ferns  and  gymuosperms  :  the  Common  Polypody  (Poly- 
podium  vulgare,  L.\  the  Maidenhair  Fern  (Adiantum  pedatum, 
L.),  the  Venus-hair  Fern  (Adiantum  capillus-veneris,  L.),  the 
Shield  Fern  (Aspidium  acrostichoides,  Swartz.),  the  Royal  Fern 
(Osmunda  regalis,  L.),  and  the  Ginkho  Tree  (Salisburia  adianti- 
folia,  Sm.).  (c)  Leaves  of  the  following  monocotyls :  the  Wan- 
dering Jew  (Callisia  repens,  Willd.),  the  Lily  of  the  Valley 
(Convallaria  majalis,  L.),  the  Clintonia  (Clintonia  borealis,  Raf.\ 
the  Bell-wort  (Uvularia  grandiflora,  Smith),  Solomon's  Seal  (Poly- 
gouatum  giganteum,  Dietrich),  the  Egyptian  Calla  (Richardia 
africana,  Kunth.),  and  the  Palmetto  (Sabal  Palmetto,  R.  and  S.). 
(d)  Leaves  of  the  following  dicotyls :  the  Common  Deutzia 
(Deutzia  scabra,  L.),  the  Beech  (Fagus  ferruginea,  Ait.),  the 
Chestnut  (Castanea  sativa,  Mill.,  var.  Americana),  the  English 
Ivy  (Hedera  helix,  L.),  the  Sugar  Maple  (Acer  saccharinum, 
Wang.),  the  Common  Mallow  (Malva  rotundi folia,  L.),  the  Wild 
Yam  (Dioscorea  villosa,  L.),  the  Common  Plantain  (Plantago 
major,  L.),  and  the  Begonia  (Begonia  nitida,  Willd.). 
\  (1)  A  Moss  Leaf. — Selecting  a  leaf  from  one  of  the  plants  men- 
tioned in  list  a,  and  examining  it  under  a  magnifying-glass,  it 
will  be  found  exceedingly  simple  in  structure  as  compared  with 
that  of  the  Geranium.  In  no  moss  or  liverwrort  is  to  be  found 
any  differentiation  of  the  leaf  into  petiole,  blade,  and  stipules. 
There  may  be  traced  with  a  magnifying-glass,  or  in  some  species 
even  with  the  naked  eye,  a  very  delicate  network  pervading  the 
leaf,  and  this  at  first  might  be  mistaken  for  the  venation  ;  but  it 


90  LABORATORY    EXERCISES    IN    BOTANY. 

is  only  the  reticulate  appearance  produced  by  the  walls  of  the  rather 
lai-v  <vlls  composing  the  leaf.  These  cells  are  not  of  many  differ- 
ent kinds,  as  in  the  higher  plants,  but  are  all  nearly  alike  and 
mostly  arranged  in  a  single  layer.  There  is  no  differentiation 
into  epidermis  and  mesophyll,  and  in  many  cases  not  even  the 
beginning  of  a  differentiation  into  veins.  This  is  true  of  the  lenfy- 
st-  mined  liverworts  generally,  and  true  of  many  mosses;  but  some 
of  the  latter  group  possess  a  very  simple  venation,  usually  con.-ist- 
in--  of  a  single  vein  or  rib  running  from,  base  to  apex  of  the  leaf, 
88  shown  on  Plate  XII.  The  cells  here  are  usually  more  than  one- 
layered,  and  more  elongated  than  the  rest,  but  are  otherwise  sim- 
ilar to  them.  There  is  no  development  of  fibrous  tissues  or  ducts, 
such  as  occur  in  the  veins  of  the  leaves  of  the  higher  plants,  and 
the  cells  contain  chlorophyll  like  the  rest. 

Here,  so  to  speak,  the  venation,  as  well  as  the  whole  leaf-struc- 
ture, is  reduced  to  its  simplest  terms. 

(2)  Forked  or  Furcate  Venation. — This  is  illustrated  in  the 
great,  majority  of  ferns  and  in  some  gymnosperms,  and  is  a 
lon-^  step  in  advance  of  the  venation  in  mosses.  Let  it  be  stud- 
ied as  it  is  found  in  the  leaf  of  Osmunda  regalis.  The  leaves 
are  laru<«  and  bipinnately  compound,  but  it  is  the  venation  of  the 
leaflet  that  one  desires  to  study.  The  leaflet  has  all  the  parts — 
epidermis,  veins,  and  mesophyll — that  were  observed  in  the  leaf 
of  the  Geranium.  In  fact,  the  leaves  of  ferns  approximate  very 
closely  in  the  complexity  of  their  structure  those  of  the  highest 
plants,  but  the  venation  is  simpler.  It  will  be  seen  that  there  is 
a  middle  vein,  called  the  midrib,  running  from  the  base  to  the 
ap.'.x.  Lateral  branches  pass  off'  from  this  on  either  side,  and 
tht-M-  again  branch  ;  and  here  in  their  mode  of  branching  is  their 
distinctive  characteristic:  they  branch  by  forking,  and  not  in  the 
ordinary  way;  that  is,  the  vein  separates  at  its  end  into  two 
eijiial  parts,  one  or  both  of  which  may  again  fork  in  the  same 
way.  Moreover,  it  is  to  be  observed  that  these  branches  remain 
distinct,  and  do  not  connect  with  other  branches  to  form  a  net- 
work. This  general  plan  is  called  the  furcate  or  forked  plan  of 
venation,  ami  this  particular  variety  of  it  is  termed  the  pinni- 
fnri'tifi;  or  pinnately  forked,  since  the  branching  somewhat  resem- 
bles that  of  a  leather. 

Another  variety  of  furcate  venation  is  illustrated  in  the  leaf 


TYPES  OF  LEAF- VENATION.  91 

of  Salisburia  adiantifolia  (PL  XL).  Here  the  secondary 
branches  of  the  venation  do  not  come  off  from  a  midrib  as  in 
Osmuuda,  but  several  veins  originate  in  the  petiole,  and,  diverg- 
ing and  repeatedly  forking,  radiate  toward  the  expanded  margin 
of  the  leaf.  This  variety  may  be  distinguished  from  the  other 
by  the  term  palmi-furcate. 

In  some  of  the  higher  ferns — as,  for  example,  Camptosorus, 
Woodwardia,  and  Onoclea — some  of  the  branches  of  the  furca- 
tions may  coalesce  with  those  of  adjacent  veins,  and  so  form  a 
kind  of  network,  thus  forecasting,  so  to  speak,  the  reticulate  mode 
of  venation,  which  will  be  studied  farther  on.  This  sort  of  net- 
fwork,  however,  should  not  be  confounded  with  that  which  is  so 
common  in  the  higher  plants,  and  really  originates  in  a  different  way. 

(3)  The  Nerved  or  Parallel  Venation. — Let  this  be  studied  first 
in  the  Wandering  Jew  (Callisia  repens),  a  common  garden  and 
greenhouse  plant,  the  leaves  of  which  are  so  transparent  that 
the  veins,  even  the  more  minute  ones,  are  readily  seen.  A  branch 
of  the  plant  is  shown  on  Plate  XII.  The  two-ranked,  sheathing, 
ovate-lanceolate  leaves  are  each  provided  with  numerous  appa- 
rently simple  veins  which  spring  from  the  base  and,  running 
somewhat  parallel  to  each  other,  terminate  in  the  apex.  Be- 
cause the  veins  appear  simple,  somewhat  like  nerves  in  form, 
though  of  course  not  in  function,  the  type  has  been  called  the 
nerved  type.  A  very  close  inspection  under  a  magnifying-glass 
will  show,  however,  that  the  veins  are  not  really  simple.  There 
will  be  discovered  minute  branches  crossing  at  intervals  from  one 
vein  to  adjacent  ones,  forming  thus  a  somewhat  regular  network 
composed  of  quadrangular  meshes.  This  is  shown  on  Plate  XIII., 
which  represents  a  part  of  one  of  the  leaves  magnified  about  two 
and  a  half  diameters.  This  reticulum  is  wholly  different  from 
that  occurring  in  a  truly  reticulate  leaf. 

Another  thing  will  be%  observed  about  this  mode  of  venation  if 
the  leaf  be  closely  inspected  with  a  glass — namely,  the  fact  that 
thicker  veins  alternate  somewhat  regularly  with  thinner  and  less 
developed  ones. 

There  are  three  varieties  of  this  mode  of  venation.  The  leaf 
just  studied  represents  one  of  them,  the  basi-nerved,  appropriately 
so  called  because  the  veins  originate  at  the  base  of  the  leaf  and  run 
to  the  apex. 


92  LABORATORY    EXERCISES   IN   BOTANY. 

Another  variety  of  nerved  venation  is  observed  in  a  few  plants, 
especially  in  some  palms.  Here  the  veins,  originating  at  the  base, 
do  not  terminate  in  a  narrow  apex,  but  diverge  in  a  radial  or  pal- 
mate manner  to  an  expanded  margin.  Hence  this  mode  of  vena- 
tion has  been  called  the  palmi-nerved. 

The  third  variety  is  the pinni-nerved,  illustrated  in  the  leaf  of  the 
Calla  and  in  that  of  the  Banana.  Here  the  veins  do  not  all  orig- 
inate in  the  base  of  the  blade,  but  run  from  a  midrib  to,  or  nearly 
to,  the  margin.  The  lateral  veins  have  substantially  the  same 
character  and  arrangement  as  those  of  basal  origin  in  the  other 
leaves  just  described.  In  some  plants  having  this  type  of  vena- 
tion, besides  the  minute  cross-veinlets,  the  main  nerves  send  out 
larger  branches  at  their  ends,  which  unite  with  similar  ones  from 
adjacent  nerves  to  form  a  continuous,  usually  wavy,  submarginal 
vein  running  from  the  base  to  the  apex  of  the  leaf.  This  is  the 
case  with  the  leaflets  of  the  Indian  Turnip  (ArisaBma  triphyl- 
lum). 

The  nerved  mode  of  leaf-venation  is  by  far  the  most  common 
among  monocotyls,  the  chief  exceptions  occurring  in  the  Arum 
and  Yam  families,  where  the  leaves  are  mostly  reticulate.  Most 
gymuosperms  also  have  nerved  leaves. 

(4)  The  Reticulate  or  Netted  Mode  of  Venation. — This,  in  one  of 
its  varieties,  may  be  studied  in  the  leaf  of  Deutzia  scabra,  L.  Here 
it  will  be  observed  that  the  larger  veins  break  up  by  repeated 
lateral  branching  into  finer  and  finer  divisions,  and  that  these 
anastomose  with  adjacent  branchlets,  forming  a  complicated  and 
more  or  less  irregular  network,  very  different  in  its  character 
from  such  a  network  as  has  been  seen  in  a  nerved  leaf,  and  also 
very  different  from  that  which  occurs  in  some  ferns.  The  vena- 
tion of  a  part  of  Deutzia  leaf,  magnified  four  diameters,  is  shown 
on  Plate  XIII. 

It  often,  though  not  always,  happens  in  this  type  of  venation 
that  the  free  end  of  a  veinlet  terminates  in  the  interior  of  a  mesh, 
as  in  the  example  now  being  studied,  or  as  is  even  more  beauti- 
fully shown  in  the  leaf  of  Cobsea  scandens,  illustrated  on  pa;j,e 
196  of  the  College  Botany. 

It  frequently  happens  also  that  a  marginal  sub-vein  is  formed 
by  the  coalescence  of  veinlets  near  the  edge  of  the  leal'. 

Manifestly,  this  mode  of  venation  is  the  most  effective,  both  as 


TYPES   OF   LEAF-VENATION.  93 

a  support  and  as  a  means  of  distributing  nutriment  to  the  meso- 
phyll  cells,  and  it  is  found,  as  would  naturally  be  expected,  the 
prevalent  mode  of  venation  in  the  highest  group  of  plants,  the 
dicotyls. 

(a)  The  pinni-reticulate,  or    piunately-netted,  venation    is  the 
particular  variety  represented  in  the  leaf  of  Deutzia.     It  has  a 
main  rib  or  midrib  running  from  base  to  apex,  from  which  issue 
laterally  the  ribs;  these  in  turn  send  oif  veins,  and  these  branch 
into   veinlets.      It  is  the  possession  of  a  midrib  which  specially 
distinguishes  this  variety  from  the  others  of  the  type. 

(b)  TJie  Palmi-reticulate  Leaf. — This  is  well  illustrated  in  the 
Common   Ivy  (Hedera  helix,   PL   XII.),   and    is  distinguished 
from  the  preceding  by  the  fact  that  there  are  several  large  veins 
springing  from  the  top  of  the  petiole  and  diverging  to  the  margin. 
These  branch  repeatedly  to  form  a  network  similar  to  that  already 
described.    Since  the  main  veins  are  arranged  in  a  radiating  man- 
ner, this  variety  is  also  called  the  radiately-reticulate  leaf. 

(c)  The  Costate-reticulate  or  Rib-netted  Leaf. — This  variety  is 
rarer  than  the  other  forms,  but  is  occasionally  met  with.     The 
Cinnamon  and  Wild  Yam  afford  illustrations.     The  peculiarity 
of  this  form  of  venation  consists  in  the  fact  that  two  or  more 
large  veins  spring  from  the  top  of  the  petiole,  and,  after  diverg- 
ing somewhat,  come  together  again  at  the  apex  of  the  blade,  the 
spaces  between  being  filled  with  a   network    similar  to  that  in 
other  reticulate  forms. 

The  reticulate  type  is  pre-eminently  that  found  among  dicotyls. 
Only  in  very  rare  instances  are  the  foliage  leaves  of  the  members 
of  this  group  nerved  or  parallel  veined.  Netted  veined  leaves, 
however,  differ  from  each  other  very  considerably  in  the  closeness 
of  the  network.  In  many  cases  the  meshes  are  very  intricate  and 
fine ;  in  others  the  network  is  much  less  complex  and  relatively 
coarse,  showing  even  a  close  approach  to  the  nerved  or  parallel 
forms,  and  so  in  leaf-structure  the  two  great  groups  sometimes 
overlap. 


TYPES   OF    LEAF-VENATION. 


95 


TYPES   OF    LEAF-VENATION. 


97 


PLATE  XII.,  FIG.  1.— Branch  of  Callisia  repens,  showing  sheathing,  two-ranked  leaves 
which  are  basi-nerved  in  their  venation  (%  natural  size). 

FIG.  2.— Leaf  of  Hedera  helix,  showing  palmi-reticulate  venation  (%  natural  size). 

FIG.  3. — Leaf  of  Moss  (magnified  about  15  diameters),  showing  that,  with  the  excep- 
tion of  the  midrib,  it  is  composed  of  a  one-layered  sheet  of  similar  cells. 

7 


TYPES   OF   LEAF-VENATION. 


99 


PLATE  XIII.,  FIG.  1.— Part  of  Leaf  of  Deutzia  scabra,  showing  pinni-reticulate  vena- 
tion (magnified  about  6  diameters). 

FIG.  2.— Portion  of  Leaf  of  Callisia  repens  (enlarged  about  4  diameters),  showing 
nerves  and  cross-veinlets. 


EXERCISE  XL 

THE  BRANCHING  OF  LEAVES. 

THE  leaves  of  the  following  plants  may  be  studied  and  com- 
pared :  the  Basswood  (Tilia  Americana,  £/.),  the  Dandelion 
(Taraxacum  officinale,  Weber),  the  White  Oak  (Quercus  alba, 
L.),  the  Shepherd's  Purse  (Capsella  bursa-pastoris,  Moench),  the 
Celandine  (Chelidonium  majus,  L.),  the  Rue  (Ruta  graveolens,  L.\ 
the  Smooth  Rose  (Rosa  blanda,  Ait.),  the  Silver  Weed  (Poten- 
tilla  anserina,  L.),  the  Trumpet  Creeper  (Tecoma  radicans,  Juss.\ 
Common  Polypody  (Polypodium  vulgare,  L.),  the  American 
Mountain  Ash  (Pyrus  Americana,  DC.),  the  Agrimony  (Agri- 
monia  parviflora,  Ait.),  the  Silver  Maple  (Acer  dasycarpum, 
Ehrh.\  the  Cranesbill  (Geranium  maculatum,  L.),  the  Castor 
Bean  (Ricinus  commuuis,  L.),  the  Summer  Grape  (Vitis  aestivalis, 
Michx.),  the  Strawberry  (Fragaria  Virginiana,  Mill.),  the  Cinque- 
foil  (Potentilla  Cauadensis,  L.),  and  the  Meadow  Rue  (Thalictrum 
dioicum,  L.). 

In  comparing  different  leaves  it  will  be  found  that  some  have 
blades  composed  of  a  single  piece,  and  that  this  is  entire  or  plain- 
margined  ;  in  others  the  blade  is  more  or  less  wavy,  scalloped,  or 
toothed  in  various  ways ;  in  still  others  the  indentation  becomes 
so  deep  as  evidently  to  forecast  those  forms  in  which  the  blade  is 
separated  into  several  distinct  pieces,  as  in  the  Clover  leaf  already 
studied,  the  more  deeply  indented  forms  being  variously  described, 
according  to  the  character  or  depth  of  the  indentations,  as  incised, 
cleft,  parted,  or  divided ;  and,  lastly,  there  are  the  truly  compound 
forms,  where,  as  in  the  Locust  and  Rose,  the  blade  is  separated 
into  two  or  more  distinct  pieces. 

Between  the  blade  that  is  barely  toothed  on  its  margin  and  the 
one  that  is  compound  there  is  every  possible  gradation.  Even  on 
the  same  plant  there  may  sometimes  be  found  leaves  that  are 
entire  or  nearly  so,  and  others  that  are  very  much  divided  or  even 
compound.  In  the  Cruci  ferae  or  Cress  family  numerous  examples 

101 


102  LABORATORY   EXERCISES   IN    BOTANY. 

of  this  kind  are  met  with,  and  in  many  aquatics  the  floating  leaves 
or  those  borne  above  the  water  are  either  entire  or  but  slightly 
segmented,  while  the  submerged  leaves  of  the  same  plant  are 
separated  into  exceedingly  numerous  and  very  fine  divisions. 

In  the  division  or  compounding  of  the  leaf-blades  the  plan 
always  follows  that  of  the  venation :  if  the  leaf  is  pinnately 
veined,  tne  leaflets  or  segments  will  be  pinnately  arranged ;  and 
if  the  venation  is  palmate  or  radiate,  the  leaflets  or  segments  will 
be  palmately  arranged. 

The  leaves  of  dicotyls  and  ferns  show  a  much  stronger  tendency 
toward  branching  forms  than  do  those  of  monocotyls  and  gym  no- 
sperms. 

Let  the  following  leaves  be  studied  by  way  of  illustration  : 

(1)  Leaf  of   Dandelion. — The   blade   is   oblanceolate,   acute, 
tapering  into  a  short   petiole,   membranous   and   herbaceous  in 
texture,  somewhat  pubescent  on  its  two  surfaces  and   strongly 
so  on  the  prominent  midrib  below,  and  its  venation  is  pinni-retic- 
ulate.     It  is  clearly  a  simple  leaf,  but  shows  a  plain  tendency  to 
the  division  or  branching  of  its  blade.     Its  marginal  incisions  are 
much  more  irregular  than  are  those  of  most  leaves,  the  teeth  vary- 
ing in  size,  in  inclination,  and  in  distance  apart.    The  sharp,  some- 
what hooked,  and  irregular  character  of  the  teeth  bears  some  re- 
semblance to  the  teeth  of  a  lion  or  other  carnivorous  animal,  and 
this  fact  explains  the  origin  of  several  of  the  names  the  plant  has 
borne — Leontodon,  Dens-leonis,  and  the  common  name  Dandelion. 
Such  a  word  as  incised  does  not  fully  describe  a  margin  like  this, 
since  many  of  the  teeth  incline  backward  or  are  hooked  in  that 
direction  ;  hence,  owing  to  the  desirability  of  making  descriptive 
terms  as  brief  and  precise  as  possible,  the  term  rundnate  has  been 
applied  to  it.     The  leaf  is  shown,  one-half  natural  size,  on  Plate 
XIV.  (Fig.  1). 

(2)  Leaf  of  the  Trumpet  Creeper. — Here  the  leaf  also  consists 
of  blade  and  petiole,  the  stipules,  as  in  Dandelion,  being  absent; 
l)iii  the  blade  is  obviously  separated  into  seven  distinct  bladelets, 
and  is  therefore  compound.    One  must  not  conclude,  though,  that 
every  leal'  which  is  separated  into  segments  to  the  midrib  is  to  be 

ided  as  compound.  If  the  segment  is  not  contracted  at  its 
base,  <>r  if  somewhat  contracted,  but  not  so  much  so  as  to  prevent 
the  green  pulp  of  the  segment  from  joining  the  midrib  or  rachis, 


THE   BRANCHING    OF    LEAVES.  103 

it  is  still  regarded  as  simple  and  is  called  a  divided  leaf.  But  if 
the  leaflets  are  distinctly  stalked,  or  if,  whether  stalked  or  sessile, 
they  are  connected  with  the  rachis  by  a  joint,  or  even  if,  possess- 
ing neither  stalk  nor  joint,  they  are  so  strongly  contracted  at  the 
base  as  to  separate  the  leaf-pulp  from  the  rachis,  the  leaf  is 
regarded  as  compound. 

In  the  compound  leaf  the  part  corresponding  to  the  midrib  of 
the  simple  leaf,  if  present,  is  called  the  rachis  ;  the  stalks  of  the 
leaflets  which  join  them  to  the  rachis  are  called  the  petiolules  ;  and 
one  of  the  leaflets  is  called  afoliole  or  foliolum. 

In  the  leaf  of  the  Trumpet  Creeper,  shown  on  Plate  XIV. 
(Fig.  2),  a  is  the  petiole,  b  is  the  rachis,  c  is  the  petiolule  of  the 
terminal  foliole.  The  leaf  is  pinnately  compound,  since  its  leaflets 
are  arranged  along  a  lengthened  rachis ;  but,  this  leaf  having  an 
odd  terminal  leaflet,  it  is  important  to  distinguish  it  from  a  pinnate 
leaf  having  an  even  number  of  leaflets,  so  it  is  called  an  impari- 
pinnate  leaf.  The  leaflets  may  be  described  as  would  be  the  blades 
of  a  simple  leaf.  In  this  instance  they  are  ovate  in  general  out- 
line, obtuse  at  the  base,  acute  or  acuminate  at  the  apex,  and 
coarsely  serrate  on  the  margin.  The  venation  is  pinni-reticulate, 
the  texture  membranous  and  herbaceous,  and  the  surface  glabrous. 

It  should  be  observed  that  the  leaves  of  this  species  commonly 
possess  either  nine  or  eleven  leaflets. 

(3)  The  Leaf  of  the  Silver  Maple. — Here,  as  in  the  Dandelion, 
may  be  found  the  simple  leaf  tending  to  a  compound  form,  but, 
the  venation  being  palmate  instead  of  pinnate,  and  there  being 
five  main  veins  radiating  from  the  top  of  the  petiole,  the  blade  is 
parted  into  five   radiating   main  divisions  or  lobes.     Since  the 
principal   incisions   extend   from   an   imaginary  general    outline 
rather  more  than  halfway  to  the  top  of  the  petiole,  the  blade 
may  be  described  as  palmately  five-cleft.     To  this  description  of 
the  margin,  however,  to  render  it  complete,  must  be  added  the 
statement  that  the   segments  are   incised   and   serrately  toothed. 
The  leaf  is  also  petiolate,  exstipulate,  cordate,  membranous  and 
herbaceous,  glabrous  on  the  ventral  surface,  and  both  pubescent 
and  glaucous  on  the  dorsal  surface.     The  leaf  is  shown,  one-half 
natural  size,  on  Plate  XIV.  (Fig.  3). 

(4)  The  Leaf  of  the  Lupine. — This  leaf  is  complete,  having 
lamina,  petiole,  and  stipules.     The  stipules  are  adnate  at  the  base 


104  LABORATORY    EXERCISES   IN   BOTANY. 

and  free  above.  They  are  linear  and  entire.  The  petiole  is 
elongated  and  somewhat  channelled  on  the  upper  surface  toward 
its  base,  and  from  its  apex  radiate  the  numerous  leaflets,  which 
vary  in  number  from  seven  to  eleven  or  more.  These  are  sessile, 
jointed  to  the  petiole,  pinnately  reticulate,  oblanceolate  in  outline, 
mucronate  at  the  apex,  entire-margined,  membranous-herbaceous 
in  texture,  and  pubescent  above  and  below — as,  in  fact,  are  also 
the  other  parts  of  the  leaf. 

Such  a  leaf  as  that  illustrated  on  Plate  XIV.  (Fig.  4)  might  be 
briefly  described  as  a  palmately  octo-foliolate  leaf,  or,  still  more 
briefly,  as  an  octonate  leaf. 


THE    BRANCHING   OF   LEAVES. 


105 


PLATE  XIV.,  FIG.  1.— The  Runcinate  Leaf  of  the  Common  Dandelion. 
FIG.  2.— The  Impari-pinnate  Leaf  of  the  Trumpet  Creeper:  a,  petiole  of  leaf ;  &,rachis  ; 
c,  petiolule  of  terminal  leaflet. 
FIG.  3.— Palmately-cleft  Leaf  of  the  Silver  Maple. 
FIG.  4.— The  Octonate  Leaf  of  the  Common  Lupine.   (All  of  the  figures  K  natural  size.) 


EXERCISE  XII. 

STUDY  OF  SOME  SPECIALLY-MODIFIED  LEAVES. 

SELECTIONS  may  be  made  from  the  following  plants :  the 
Locust  (Robin  ia  Pseudacacia,  L.),  the  Common  Green  brier 
(Smilax  rotundifolia,  Z.),  the  Beach  Pea  (Lathyrus  maritimus, 
Biyelow\  the  Yellow  Vetchling  (Lathyrus  Aphaca,  L.\  the 
Prickly  Pear  (Opuutia  Rafinesquii,  Englm.\  the  Butterwort 
(Pinguicula  vulgaris,  L.\  the  Bladderwort  (Utricularia  vulgaris, 
L.),  the  Round-leaved  Sundew  (Drosera  rotundifolia,  L.)  or  the 
Long-leaved  Sundew  (Drosera  intermedia,  Hayne.,  var.  Ameri- 
cana, DC.),  Venus's  Fly-trap  (Dionsea  muscipula,  Ellis),  the 
Pitcher-plant  (Sarracenia  purpurea,  Z/.),  the  Trumpet-plant  (Sar- 
racenia  flava,  Z.),  and  the  East  Indian  Pitcher-plant  (Nepenthes 
ampullaria,  Jack.). 

Observation  has  already  been  made  of  leaves  under  their  ordi- 
nary forms — namely,  as  foliage,  and  also  variously  disguised  as 
bud-scales,  as  bulb-scales  both  fleshy  and  membranous,  as  rhizome- 
scales,  and  as  tuber-scales.  But  there  are  various  other  disguises 
or  modifications  which  they  assume,  fitting  them  for  as  various 
uses.  In  fact,  no  organ  of  the  plant  presents  itself  under  such  a 
variety  of  forms  or  serves  such  a  variety  of  uses.  Leaves  are 
sometimes  wholly  or  partly  modified  into  spines  for  defence,  into 
tendrils  for  climbing,  into  pitchers  and  traps  for  catching  insects, 
and  into  the  various  organs  of  the  flower — sepals,  petals,  stamens, 
and  pistils  to  subserve  the  functions  of  reproduction. 

For  this  study  a  selection  is  made  of  two  leaves  which  serve  to 
entrap  insects — those  of  Sarracenia  purpurea  and  those  of  Drosera 
rotundifolia. 

(1)  The  Pitcher-plant  is  not  uncommon  in  our  northern  bogs. 
Its  pitcher-shaped  leaves  are  all  radical,  and  form  a  tuft  or  rosette 
with  their  apices  pointing  upward.  From  the  centre  of  the  mass 
of  leaves  rises  the  usually  solitary  scape  to  the  height  of  about  a 
foot ;  this  scape  bears  the  conspicuous,  nodding,  pentamerous,  pur- 

107 


108  LABORATORY    EXERCISES   IN   BOTANY. 

pie  flowers,  which  are  remarkable  for  the  large,  shield-shaped,  five- 
pointed,  persistent  stigmas. 

Each  leaf  consists  of  an  upper  part  (PI.  XV.  Fig.  1,  a),  called 
the  lip  ;  a  hollow  portion  (6)  which  is  usually  filled,  or  partly  so, 
with  water,  and  which  may  be  called  the  bowl ;  a  flattened  expan- 
sion (c)  on  the  ventral  surface,  called  the  wing  ;  and  a  short  stalk 
(d).  The  venation,  it  will  be  observed,  is  costate-reticulate ;  the 
exterior  of  the  pitcher  is  smooth,  more  or  less  purple-blotched, 
and  slightly  glandular  along  the  wing.  The  interior  is  partly 
hairy  and  partly  very  smooth,  and  the  water  may  usually  be 
observed  to  contain  the  remains  of  numerous  insects  in  various 
stages  of  decomposition. 

It  is  not  easy  to  trace  the  structural  relations  between  this  and 
an  ordinary  leaf,  but  there  are  reasons,  derived  from  analogy  and 
from  the  study  of  the  very  young  leaves,  for  believing  that  the 
lip  represents  the  lamina,  and  the  rest,  including  the  wing,  bowl, 
and  stalk,  represents  the  petiole.  The  petiole  is  thus  analogous  to 
the  vertically  flattened  ones,  called  phyllodia,  of  the  Australian 
acacias,  differing  from  them  chiefly  in  the  fact  that  a  part  of  it- 
has  become  hollow.  In  the  very  young  leaf,  however,  the  hollow 
does  not  exist,  and  the  analogy  is  then  closer  still. 

The  stipules  are  not  present,  unless  the  lateral  widening  at  the 
base  of  the  petiole  may  be  regarded  as  due  to  stipules  which  have 
become  adnate. 

The  water  found  in  the  bowl  may  partly  be  caught  from  rains ; 
but  it  cannot  be  wholly  so,  for  it  is  present,  though  in  diminished 
quantity,  even  in  dry  weather  and  in  pitchers  which  have  not 
yet  opened.  Moreover,  in  some  other  Sarracenias,  and  in  Dar- 
lingtonia,  a  California  relation  of  the  genus,  the  orifice  is  pro- 
tected from  the  entrance  of  rain,  and  yet  water  in  considerable 
quantity  is  usually  present  in  the  bowl.  The  water  is  therefore 
partly  a  secretion  of  the  plant.  Besides  the  fact  that  in  this 
water,  when  the  leaf  is  mature,  are  usually  to  be  found  in  great 
numbers  insects  drowned  and  in  various  stages  of  putrefaction, 
there  is  much  other  evidence  to  show  that  the  leaf  is  adapted  to 
the  function  of  insect-trapping,  the  plant  making  use  of  the  cap- 
tured creatures  for  food.  This  is  shown  not  only  by  the  structure, 
but  by  direct  observation  of  the  process  of  capture,  which  may 
readily  be  seen  where  the  plants  are  abundant. 


STUDY   OF   SOME   SPECIALLY-MODIFIED    LEAVES.  109 

It  will  be  noted  that  the  lip  on  its  upper  or  ventral  surface  is 
provided  with  numerous  stiff,  sharp,  and  downwardly-pointing 
hairs,  which  do  not  much  interfere  with  the  progress  of  an  insect 
toward  the  interior  of  the  bowl,  but  present  a  decided  obstacle  to 
its  progress  in  the  opposite  direction.  These  hairs  disappear  at 
or  near  the  throat  of  the  pitcher,  and  the  interior  becomes  exceed- 
ingly smooth,  forming  a  surface  on  which  the  footing  of  even  a 
fly  or  an  ant  is  very  insecure.  The  throat  is  also  somewhat  con- 
tracted, making  it  difficult  for  an  insect,  when  once  inside,  to  fly 
outward.  The  smooth  area  extends  downward  half  or  two-thirds 
the  length  of  the  bowl,  and  is  then  succeeded  by  an  area  covered 
with  longer  and  more  slender  downwardly-pointing  hairs.  These 
serve  to  entangle  insects  that  fall  into  the  water,  and  so  hasten 
their  drowning. 

But  the  trap  is  also  baited.  Along  the  wing  and  about  the 
throat  on  the  inside  of  the  pitcher  there  exudes  a  sweet  secretion 
which  entices  insects  to  the  slippery  interior  surface,  and  thus 
renders  their  destruction  nearly  certain.  It  was  at  one  time  sup- 
posed that  this  secretion  had  an  intoxicating  effect,  but  this  has 
not  been  proven. 

Whether  or  not  the  other  secretion  at  the  bottom  of  the  bowl 
contains  any  specially  digestive  principle  has  not  yet  been  deter- 
mined with  certainty,  though  probably  it  does  not.  But  the 
decaying  bodies  of  the  insects  doubtless  form  a  nutritious  mixture 
which  is  to  some  extent  absorbed  by  the  leaves  and  nourishes  the 
plant. 

Experiment  seems  to  show  that  the  water,  even  when  first 
secreted,  possesses  greater  asphyxiating  power  upon  insects  than 
does  rain-water,  probably  by  reason  of  its  more  readily  wetting 
their  spiracles.  What  the  constituents  are  that  give  it  this  prop- 
erty is  not  known. 

The  Pitcher-plant  is  therefore  certainly  insectivorous,  and  most 
insects  that  frequent  marshy  places  are  liable  to  be  captured  by  it. 
But  there  are  at  least  two  curious  exceptions — a  species  of  moth 
and  a  species  of  fly.  These  insects  are  exceptional  among  their 
kind  in  having  in  their  feet  hooks  sufficiently  long  and  sharp  to 
enable  them  to  cling  securely  to  the  smooth  interior  walls.  Both 
species  deposit  their  eggs  in  the  putrid  contents  of  the  pitcher, 
and  the  larvae  feed  and  fatten  upon  the  putrescent  matters  until 


110  LABORATORY    EXERCISES    IN    BOTANY. 

ready  to  assume  the  winged  condition.  The  larva  of  the  fly  even 
attacks  the  wall  of  the  pitcher  itself,  bores  holes  through  it,  and 
destroys  it.  So,  iusect-devourer  that  it  is,  like  most  other  plants, 
it  has  its  insect  enemies,  which  obtain  their  living  at  its  expense. 

(2)  The  Round-leaved  Sundew  also  grows  in  marshy  places,  and 
is  to  be  found  in  suitable  situations  over  the  whole  northern  hem- 
isphere. Its  round,  petiolate  leaves,  half  a  dozen  or  more  in 
number,  are  all  radical  and  lie  flat  upon  the  ground.  From  the 
centre  of  the  circle  there  rises,  to  the  height  of  from  three  to  five 
inches,  the  single,  slender,  erect  flower-stalk,  which  bears  a  more 
or  less  one-sided  raceme  of  inconspicuous  white  flowers. 

The  blades  of  the  leaves,  about  half  an  inch  broad,  are  thickly 
studded  on  the  margin  and  upper  surface  with  hairs  or  tentacles 
each  of  which  is  tipped  with  a  glistening  gland  which  resembles 
a  minute  drop  of  dew.  The  tentacles  are  structurally  much  more 
complex  and  better  developed  than  are  ordinary  hairs,  to  accord 
with  their  more  complex  functions. 

This  leaf  is  also  an  insect-trap,  and  a  very  perfect  one  at  that ; 
but  how  different  in  its  construction  from  that  of  the  Pitcher- 
plant  !  The  prey  consists  of  small  flies,  ants,  etc.,  that  are 
attracted  to  it  apparently  by  the  glittering,  dew-like  drops  on  the 
ends  of  the  tentacles.  These,  when  ready  to  make  their  capture, 
are  spread  out  as  shown  on  Plate  XV.  (Figs.  3  and  4,  which  are 
upper-surface  and  edge  views,  respectively,  of  one  of  the  leaves). 
An  insect  alighting  upon  the  leaf  is  nearly  certain  to  get  its  legs 
entangled  in  the  very  adhesive  droplets  at  the  ends  of  the  tenta- 
cles, and  usually  its  frantic  struggles  for  freedom  only  serve  to 
bind  it  more  securely  by  bringing  its  body  into  contact  with 
more  of  the  glands.  But  the  tentacles  are  far  from  being  merely 
mechanical  in  their  action  :  they  are  endowed  with  an  exquisite 
sensitiveness  and  with  the  power  of  movement  in  response  to 
stimulus.  Even  a  minute  food-particle  placed  on  the  end  of  one 
of  the  exterior  tentacles  causes  it  to  bend  slowly  but  surely  over 
toward  the  centre  of  the  leaf.  Not  only  this,  but  the  stimulus  is 
transmitted  to  adjacent  tentacles,  which  also  bend  in  the  same  di- 
rection, and  if  the  object  be  of  considerable  size — say  as  larire  ;i-  a 
<rnat — all  the  tentacles  may  become  involved  in  these  movement-. 
Tin-  insect  is  thus  carried  to  the  centre  of  the  leaf,  and  the  leaf 
itself  finally  rolls  inward  to  some  extent,  so  that  the  unfortunate 


STUDY   OF   SOME   SPECIALLY-MODIFIED   LEAVES.  Ill 

creature  becomes  nearly  or  wholly  enveloped,  and  of  course 
asphyxiated. 

Charles  Darwin,  who  gave  this  plant  a  most  careful  study, 
experimented  on  the  sensitiveness  of  the  tentacles,  and  found 
that  a  bit  of  human  hair  weighing  only  y-gy^Q-  of  a  grain,  placed 
upon  a  gland,  was  sufficient  to  cause  the  tentacles  to  sweep 
through  an  angle  of  180° ;  and,  even  more  remarkable  than 
this,  he  found  that  less  than  a  millionth  of  a  grain  of  phosphate 
of  ammonia  in  solution  sufficed  to  produce  similar  movements. 

Not  less  strange  and  wonderful  is  the  digestive  process  which 
supervenes.  The  insect  being  secured  at  the  centre  of  the  leaf, 
the  secretion  of  the  tentacles  now  changes  its  character,  becoming 
less  viscid  than  before,  acid  in  its  reaction,  and  containing  some 
digestive  principle  analogous  to,  if  not  identical  with,  pepsin. 
This  secretion  is  poured  out  copiously  over  the  victim's  body, 
and  digestion  goes  on  until  there  is  nothing  left  of  it  but  the  in- 
soluble skeleton.  After  this  the  leaf  gradually  unrolls,  the  ten- 
tacles straighten  out,  the  glands  again  secrete  the  viscid  droplets, 
and  all  is  in  readiness  for  another  capture. 

It  has  been  further  proven  beyond  peradventure  that  the  dis- 
solved or  peptonized  albuminous  materials  are  absorbed  into  the 
interior  of  the  leaf  and  appropriated  by  its  cells.  The  plant,  in 
fact,  digests  and  assimilates  in  truly  animal  fashion.  While,  how- 
ever, it  profits  by  an  animal  diet,  it  is  not  wholly  dependent  on 
one,  for  the  leaves  still  contain  abundance  of  chlorophyll,  which, 
as  in  other  plants,  enables  it  to  assimilate  carbon  dioxide  from 
the  atmosphere. 


STUDY   OF   SOME   SPECIALLY-MODIFIED   LEAVES.  113 


PLATE  XV.,  FIG.  1.— Leaf  of  Sarracenia  purpurea  (%  natural  size) :  a,  lip ;  b,  bowl;  c, 
wing ;  d,  stalk,  or  lower  part  of  petiole. 

FIG.  2.— The  same  Leaf  cut  through  transversely,  showing  interior  cavity. 

FIG.  3.— Leaf  of  Drosera  rotundifolia  (natural  size):  a,  one  of  the  tentacles  ;  b,  petiole. 
The  figure  shows  the  upper  surface,  the  lower  surface  not  being  provided  with  tentacles. 

FIG.  4.— Edge  view  of  Leaf  of  Drosera. 
8 


STUDY    OF   SOME   SPECIALLY-MODIFIED    LEAVES. 


115 


PLATE  XVI.— Pitcher-like  Insect-trap  of  one  of  the  East  Indian  Pitcher-plants, 
Nepenthes  Chelsoni  (%  natural  size).  The  lower  part,  a  small  portion  of  which  is 
seen  afc  a,  is  flat,  like  an  ordinary  leaf-blade,  and  serves  the  same  purpose.  The  mid- 
dle portion  is  developed  into  a  tendril,  6,  which  serves  the  purpose  of  climbing,  and 
at  the  end  of  this  tendril  is  developed  the  pitcher,  c,  which  serves  as  an  insect-trap. 
This  is  surmounted  by  a  lid,  d,  which  serves  to  keep  out  much  useless  extraneous 
matter  and  any  excess  of  water  from  rains,  while  permitting  the  access  of  insects.  The 
latter  are  attracted  by  sweet  secretions  on  the  lid  and  about  the  mouth  of  the  pitcher  on 
the  inside.  At  the  throat  is  a  strong  fold,  e,  bordered  with  downwardly-pointing  spines 
to  prevent  the  escape  of  the  prey.  The  inner  surface  is  provided  with  numerous  glands 
which  secrete  the  fluid  that  serves  at  once  to  drown  the  insects  and  to  digest  their  bodies. 


FOEM  FOE  THE  STUDY  OF  LEAVES. 


Tf 

Auriculate. 

Trisect. 

1.  Foliage  leaf. 
2.  Ascidium. 

Sagittate. 
Cordate. 
Obcordate. 

Quadrisect. 
Quinquesect. 
Sexisect. 

3.  Insect-trap. 

Panduriform. 

Septisect. 

4.  Spine. 

Flabelliform. 

Multisect. 

5.  Tendril. 

Peltate. 

6.  Pinnate  forms. 

6.  Scale. 
7.  Phyllodium.  • 

Reniform. 
Length. 

Incised. 
Runcinate. 

6.  Base. 

Lobate  : 

II.  PREFOLIATION. 

Acute  or  cuneate. 

Trilobate. 

1.  Reclinate. 
2.  Conduplicate. 
3.  Convolute. 
4.  Circinate. 
5.  Involute. 
6.  Revolute. 
7.  Equitant. 
8   Obvolute 

Acuminate. 
Obtuse  or  rounded. 
Truncate. 
Retuse. 
Cordate. 
Reniform. 
Auriculate. 
Hastate. 

Quadrilobate. 
Quinquelobate. 
Sexilobate. 
Septilobate. 
Multilobate. 
Lyratelv-lobed. 
Cleft  : 
Trifid. 

9.  Triquetrous. 

Sagittate. 
Oblique. 

Quadrifid. 
Quinquefid. 

C»   A.DGX. 

Sexifid. 

III.  PHYLLOTAXY. 

Acute. 

Septifid. 

1.  Whorled. 

Acuminate. 

Multifid. 

a.  Opposite. 

Obtuse. 

Lyrately-cleft. 

b.  Decussate. 

Retuse. 

Parted  : 

c.  In  threes. 

Emarginate. 

Tripartite. 

d.  In  fours. 

Obcordate. 

Quadripartite. 

e.  In  fives. 

Mucronate. 

Quinquepartite. 

/.  Leaves   numerous   in 
each  whorl. 

Cuspidate. 
A  ri  state. 

Sexipartite. 
Septipartite. 

2.  Alternate. 
a.  Distichous,    or     two- 

d.  Margin  (indentations 
shallow  or  none). 

Multipartite. 
Lyrately-parted. 

ranked. 

Entire. 

Pectinate. 

6.  Tristichous,  or  three- 

Serrate. 

Divided  : 

ranked. 

Serrulate. 

Trisect. 

c.  Pentastichous,  or  five- 

Biserrate. 

Quadrisect. 

ranked. 

Dentate. 

Quinquesect. 

d.  Octastichous,  or  eight- 

Denticulate. 

Sexisect. 

ranked. 

Bidentate. 

Septisect. 

e.  Triskaidekasticbous, 

Crenate. 

Multisect. 

or  thirteen-ranked. 

Crenulate. 

Lyratelv-divided 

/.  Twenty-one  ranked. 

Bicrenate. 
Repand. 

Bi-pinnatisect. 
Pinnately-dis- 

Undulate. 

sected. 

IV.  DURATION. 

1.  Persistent. 

Spinose. 

2.  Compound. 

2.  Deciduous. 

Crispate. 

(1)  Palmate  forms. 

3.  Fugacious. 

e.  Margin    (indentations 

a.  Binate  or  bifoliolate. 

deep). 

6.  Ternate. 

V.  POSITION. 

a.  Palmate  forms. 

c.  Biternate. 

Incised. 

d.  Triternate. 

1.  Cauline. 

Lobate  : 

e.  Quadriternate. 

2.  Rameal. 
3.  Radical. 

Bilobate. 
Trilobate. 

/.  Ternately-decom- 
pound. 

Quadrilobate. 

g.  Quadrate. 

VI.  PARTS  PRESENT. 

Quinquelobate. 

'h.  Quinate. 

1     lamina 

Sexilobate. 

i.  Sextate. 

2.  Petiole. 

Septilobate. 

j.  Septinate. 

3.  Stipules. 

Cleft  : 
Bifid. 

k.  Octate. 
1.  Palmately  multifolir 

VII.  LAMINA. 

Trifid. 
Quadrifid. 

(2)  Pinnate  forms. 

1.  Simple. 
(1)  Terete. 

Quinquefid. 
Sexifid. 

a.  Paripinnate   (numbe 
of  leaflets). 

(2)  Awl-shaped. 
(3)  Filiform. 

Septifid. 
Multifid. 

&.  linparipinnate   (num 
ber  of  leaflets). 

(4)  Flattened. 

Parted  : 

c.  Cirrhosely-pinnatc 

a.  General  outline. 
Orbicular. 
Linear. 
Oblong. 
Elliptical. 

Bipartite. 
Tripartite. 
Quadripartite. 
Quinquepartite. 
Sexipartite. 

(number  of  leaflets 
d.  Interruptedly-pinnat 
(number  of  leaflets) 
e.  Lvrate     (number     o 
'leaflets). 

Ovate. 
Obovate. 
Lanceolate. 

Septipartite. 
Multipartite. 
Pedate. 

/.  Bi  pinnate. 
g.  Tripinnate. 
h.  Quadripinnate. 

Oblanceolate. 

Divided  : 

i.  Pinnately-decom- 

Hastate. 

Bisect. 

pound. 

FORM  FOE  THE  STUDY  OF  LEAVES  (CONTINUED}. 


(3)  Shape  of  leaflet. 
a.  General  outline. 
Filiform. 

(2)  Nerved, 
a.  Basi-iierved. 
b.  Palmi-nerved. 

4.  Flattened  vertically. 
5.  Wing-margined. 
6.  Phyllodium. 

Orbicular. 

c.  Pinni-nerved. 

Linear. 

(3)  Reticulate. 

IX    STIPULES 

Oblong. 
Elliptical. 
Ovate. 

a.  Palmi-reticulate. 
b.  Pinni-reticulate. 
c.  Costate-reticulate. 

1.  Foliaceous. 
2.  Scarious. 

Obovate. 
Lanceolate. 
Cordate. 
Obcordate. 
Length. 
6.  Base. 
Acute  or  cuneate. 

4.  Texture. 
(1)  Herbaceous. 
(2)  Scarious. 
(3)  Membranous. 
(4)  Succulent. 
(5)  Coriaceous. 

3.  Caducous. 
4.  Adnate. 
5.  Half-sagittate. 
6.  Ochreate. 
7.  Forming  spines. 
8.  Forming  tendrils. 
9.  Forming  glands. 

Obtuse  or  rounded. 

5.  Surface. 

Cordate. 

(1)  Glabrous. 

X.  TASTE. 

Oblique. 
c.  Apex. 
Acute. 
Acuminate. 
Obtuse. 
Retuse. 
Obcordate. 
Mucronate. 
Cuspidate. 
Aristate. 
d.  Margin. 
Entire. 
Serrate. 
Serrulate. 
Biserrate. 
Dentate. 
Denticulate. 

(2)  Glaucous. 
(3)  Punctate. 
(4)  Glandular. 
(5)  Rugose. 
(6)  Scabrous. 
(7)  Verrucose. 
(8)  Pubescent. 
(9)  Puberulent. 
(10)  Sericeous. 
(11)  Lanuginous. 
(12)  Tomentose. 
(13)  Villose. 
(14)  Pilose. 
(15)  Floccose. 
(16)  Hispid. 
(17)  Strigose. 
(18)  Spinose. 

1.  Insipid 
2.  Bland. 
3.  Sweet. 
4.  Bitter. 
5.  Mucilaginous. 
6.  Pungent. 
7.  Acrid. 
8.  Warm. 
9.  Burning. 
10.  Cooling. 
11.  Astringent. 
12.  Nauseous. 
13.  Prickling. 
14.  Saline. 
15.  Alkaline. 
16.  Acidulous. 

Bidentate 

(19)  Echinate. 

Crenate. 

(20)  Aculeate. 

XI.  ODOR. 

Crenulate. 

6.  Insertion. 

1.  Odorless. 

Bicrenate. 

(1)  Sessile. 

2.  Faint. 

Repand. 

(2)  Clasping. 

3.  Agreeable. 

Undulate. 

(3)  Sheathing. 

4.  Aromatic. 

Sinuate. 

(4)  Perfoliate. 

5.  Mint-like. 

Spinose. 

(5)  Connate. 

6.  Balsamic. 

Crispate. 

(6)  Decurrent. 

7.  Camphoraceous. 

Incised. 

8.  Terebinthinous. 

Lobate. 
Cleft. 

VIII.  PETIOLE. 

9.  Pungent. 
10.  Musky. 

Parted. 
Divided. 

1.  Length    as    compared 
with  lamina. 

11.  Disagreeable. 
12.  Irritating. 

3.  Venation. 

2.  Flattened   on    ventral 

13.  Nauseous. 

(1)  Furcate. 

surface. 

14.  Narcotic. 

a.  Palmi-furcate. 

3.  Channelled  on  ventral 

15.  Putrid. 

b.  Pinni-furcate. 

side. 

16.  Fetid. 

EXERCISE  XIII. 
A  TYPICAL  FLOWER  OF  A  DICOTYL. 

IN  beginning  the  study  of  flowers  it  is  well  to  have  in  mind  a 
type  or  pattern  flower  with  which  all  others  may  be  compared. 
This  is  not  merely  a  great  convenience,  but  it  is  probable  that  all 
or  nearly  all  of  the  flowers  of  the  two  higher  groups  of  flowering 
plants,  the  monocotyls  and  the  dicotyls,  no  matter  how  irregular, 
defective,  or  uusymmetrical  they  may  now  be,  have  been  modified 
from  one  or  a  few  simple  structural  types.  The  study  and  com- 
parison of  a  large  number  of  flowers  have  enabled  botanists  to 
determine  with  a  good  deal  of  certainty  what  these  types  are  for 
monocotyls  and  dicotyls  respectively. 

Most  existing  flowers  have  in  the  course  of  time  been  consider- 
ably, sometimes  profoundly,  modified  from  the  type,  and  these 
modifications  exist  in  great  variety  among  different  species;  but 
there  are  still  a  few  which  conform  rather  closely  to  the  original 
plan.  From  some  of  these  the  selections  for  study  will  be  made. 

The  plan  will  be,  first,  to  take  up  a  nearly  typical  flower  from 
the  dicotyls,  and  after  its  structure  has  been  comprehended  to 
study  some  others  that  show  more  or  less  considerable  deviations 
from  the  type ;  then,  finally,  to  proceed  in  a  similar  manner  to 
the  study  of  monocotyls. 

The  following  dicotyls  produce  flowers  that  approach  quite 
closely  to  the  typical  form  :  the  Mossy  Stonecrop  (Sedum  acre, 
_L.),  the  Purple  Stonecrop  (Sedum  pulchellum,  Michx.),  the  Live- 
for-ever  (Sedum  Telephium,  £.),  the  Common  Flax  (Linum  usi- 
tatissimum,  L.},  the  Perennial  Flax  (Liuum  perenue,  L.\  the 
Wild  Cranesbill  (Geranium  maculatum,  L.),  the  Common  Wood- 
sorrel  (Oxalis  Acetosella,  L.\  the  Yellow  Wood-sorrel  (Oxalis 
corniculata,  L.). 

The  flower  of  the  Common  Flax  shall  serve  the  present 
purpose. 

The  plant  is  a  rather  slender,  erect,  somewhat  branching,  and 

117 


118  LABORATORY    EXERCISES   IN    BOTANY. 

smooth  annual  herb  which  grows  to  the  height  of  from  thirty  to 
sixty  centimetres.  Its  bast-fibres  constitute  one  of  our  most  valu- 
able textile  materials — linen — and  its  seeds  are  the  source  of  the 
very  useful  linseed  oil.  The  leaves  are  alternate,  sessile,  linear- 
lanceolate,  entire,  and  from  two  to  four  centimetres  in  length. 
The  corymbosely  arranged  branches  are  terminated  by  one-sided 
false  racemes  of  blue  flowers,  which  are  the  special  object  of  this 
study. 

(1)  The  Floral  Symmetry. — Observing  one  of  the  flowers 
closely,  it  will  be  found  to  possess  four  different  kinds  of  floral 
organs,  each  organ  representing  a  leaf,  though  quite  different 
from  ordinary  leaves  in  form,  and  the  different  kinds  being 
arranged  in  successive  circles  or  whorls.  The  outer  whorl,  called 
the  calyx,  is  composed  of  green  leaves,  each  termed  a  sepal ;  the 
second,  called  the  corolla,  is  composed  of  blue  and  much  larger 
pieces,  each  termed  a  petal ;  the  third  whorl,  called  the  andros- 
cium,  consists  of  individual  pieces  called  stamens  which  are  very 
different  from  the  other  organs  in  size  and  appearance.  Their 
function  is  to  produce  the  fertilizing  dust  called  pollen.  The 
organs  heretofore  mentioned  are  separate  from  each  other,  each 
arising  independently  of  the  others  from  the  receptacle,  but  the 
stalks  or  filaments  of  the  stamens  are  united  at  their  bases,  form- 
ing a  short  tube.  It  will  moreover  be  observed  in  many  flowers 
of  this  species  that  between  the  bases  of  each  pair  of  filaments  is 
a  small  thread-like  body.  There  are  the  same  number  of  these 
as  of  stamens — namely,  five — and  they  are  doubtless  to  be  re- 
garded as  stamens,  a  fast  disappearing  remnant  of  a  second  whorl 
of  these  organs.  They  are  technically  called  staminodes. 

Interior  to  the  androecium  is  the  innermost  floral  whorl,  consti- 
tuting the  gyncecium.  It  is,  at  the  base  at  least,  a  single  organ, 
though  its  whole  structure  shows  that  it  is  really  made  up  of 
five  leaf-elements,  or  carpels.  The  upper  parts,  in  fact,  styles 
and  stigmas,  are  still  distinct,  and  the  lower  part,  or  ovary,  shows 
by  the  fact  that  it  is  five-lined  exteriorly  and  five-celled  interiorly 
that  it  is  a  composite  body  made  up  of  five  pieces. 

It  will  be  observed  that  the  successive  whorls  alternate  with 
each  other.  For  example,  the  petals  are  not  inserted  on  the  re- 
ccpturlr  directly  in  front  of  the  sepals,  but  in  front  of  the  inter- 
spaces between  them.  The  relative  arrangement  is  shown  on  the 


A    TYPICAL    FLOWER   OF    A    DICOTYL.  119 

ground  plan  on  Plate  XVII.  (Fig.  4).  Another  noteworthy  fact 
is  the  resemblance  between  the  pieces  of  each  whorl.  These  pieces 
are  alike  in  size,  shape,  and  coloring — a  fact  expressed  by  saying 
that  they  are  regular. 

Inferences  can  now  easily  be  drawn  as  to  the  type  or  model  on 
which  the  flower  was  originally  constructed  :  (1)  It  was  five- 
whorled ;  (2)  It  was  symmetrical ;  that  is  to  say,  the  whorls 
alternated  with  each  other ;  (3)  It  was  regular ;  (4)  It  was  con- 
structed on  the  numerical  plan  of  five  ;  (5)  Its  parts  were  all  dis- 
tinct or  ununited  and  separately  inserted  on  the  receptacle. 

To  this  plan  or  type  the  flower  conforms  in  most  respects,  but 
deviates  slightly,  as  has  been  seen,  in  some :  in  the  partial  dis- 
appearance of  one  whorl  of  stamens ;  in  the  growing  together  of 
the  basal  parts  of  the  filaments ;  and  in  the  partial  union  of  tjie 
carpels  of  the  gynoecium. 

(2)  Deviations  from  the  Type. — Comparing  the  flowers  of  dif- 
ferent dicotyls  with  the  type,  various  kinds  of  deviations  from  it 
are  found. 

(a)  The  numerical  plan  is  often  different.  By  far  the  common- 
est number  among  dicotyls  is  the  number  five;  but  not  infre- 
quently the  number  four  is  met  with,  as  in  the  Cruciferse,  the 
Oleacese,  and  many  of  the  Rubiacese;  sometimes  the  number  two, 
as  in  the  PapaveraceaB  and  the  Fumariacese ;  and  sometimes  the 
number  six,  as  in  some  of  the  Berberidacese. 

In  some  instances  there  is  such  an  excessive  multiplication  of 
parts,  or,  on  the  other  hand,  such  an  extreme  reduction  of  them, 
that  the  original  numerical  plan  is  obscured.  Instances  of  the 
former  occur  in  the  Water  Lilies  and  Cactacese,  and  of  the  latter 
in  the  Willows. 

It  is  probable  that  in  some  instances  of  deviation  from  the 
number  five  the  deviation  has  come  about  by  a  reduction  of  the 
number  of  parts.  For  example,  in  the  genus  Sedum  tetramerous 
flowers  are  often  found  in  the  same  cluster  with  pentamerous  ones, 
and  there  can  be  little  doubt  that  the  tetramerism  has  been  brought 
about  as  a  gradual  modification  from  the  pentamerous  type. 

It  would  be  unsafe  to  conclude,  however,  that  all  flowers  of 
dicotyls  were  originally  constructed  on  the  plan  of  five. 

(6)  The  whorls  are  often  diminished  in  number.  The  most  com- 
monly omitted  whorl,  perhaps,  is  the  outer  or  inner  whorl  of 


120  LABORATORY   EXERCISES   IN   BOTANY. 

stamens ;  but  the  flower  may  be  defective  in  any  of  the  other 
whorls,  or  even  in  several  of  them.  It  may  be  reduced,  in  fact, 
to  a  single  whorl,  or  even  to  a  single  floral  leaf.  Thus,  there  are 
flowers  with  pistils  only  ;  those  with  stamens  only ;  those  without 
either  stamens  or  pistils ;  those  with  both,  but  without  floral  en- 
velopes ;  those  which  consist  of  a  single  stamen  or  of  a  single 
pistil;  and  so  on. 

(c)  The  whorls  are  often  increased  in  number.     This  may  apply 
to  any  of  the  floral  organs,  and  may  occur  naturally  or  may  be 
produced   artificially.      In  the  Buttercup   and    Strawberry,  for 
example,   the   stamens   and   pistils   are    multiplied    excessively, 
while  the  sepals  and  petals  conform  to  the  number  five. 

"  Double  "  Roses,  Buttercups,  and  Camellias  are  examples  of 
deviations  of  a  similar  nature  brought  about  by  a  high  degree  of 
cultivation. 

(d)  The  parts  frequently  grow  together.     A  tendency  of  this  kind 
has  been  seen  in  the  stamens  and  pistils  of  the  Flax,  but  it  is  car- 
ried much  farther  in  many  other  flowers.     Either  organs  of  the 
same  kind  may  unite,  as  in  the  Morning-glory,  where  the  five 
petals  are  merged  into  a  single  funnel-shaped  organ,  or  organs 
of  different  kinds  may  unite  more  or  less,  as  when  the  stamens 
are  borne  in  the  corolla-tube  in  the  Phlox,  or  the  stamens  and 
pistils  adhere,  as  in  the  Milkweeds. 

(e)  The  parts  may  be  irregular.     Deviations  of  this  sort  are 
exceedingly  common,  and  may  occur  in  any  organ  of  the  flower, 
though  those  which  most  commonly  show  irregularities  of  size, 
shape,  or  color  are  the  calyx  and  corolla.     There  may  be  only  a 
slight  difference  in  color,  shape,  or  size  among  organs  of  the  same 
whorl,  or  some  one  or  more  of  them  may  be  markedly  different 
from  the  rest,  as  in  the  spurred  sepal  of  the  Larkspur  or  the 
spurred  petal  of  the  Violet. 

(/)  There  may  be  anteposition  instead  of  alternation  of  parts. 
The  petals  may  be  inserted  directly  in  front  of  the  sepals,  or  the 
stamens  in  front  of  the  petals,  or  the  pistils  in  front  of  the 
stamens ;  all  or  any  of  these  varieties  of  dissymmetry  may  occur 
in  a  single  flower.  Deviations  of  this  sort  come  about  sometimes 
by  the  suppression  of  a  whorl.  If,  for  example,  there  were  orig- 
inally two  whorls  of  stamens  in  a  symmetrical  flower,  the  sup- 
pression of  the  outer  one  would  leave  the  inner  one  opposite 


A    TYPICAL   FLOWER   OF  A    DICOTYL.  121 

the  petals.  Doubtless  most  deviations  of  the  kind  may  be  ex- 
plained in  this  way,  but  sometimes  they  are  due  to  the  consolida- 
tion of  two  whorls  into  one,  as  is  probably  the  case  in  some  mem- 
bers of  the  Barberry  family. 

As  a  practical  point  of  much  importance  to  the  beginner,  it  is 
to  be  noted  that  flowers  constructed  on  the  numerical  plan  of  three 
are  much  the  commonest  among  monocotyls  and  seldom  occur 
among  dicotyls. 

The  student  should  now  study  and  make  drawings  of  one  of  the 
other  flowers  mentioned  at  the  beginning  of  this  exercise. 


A   TYPICAL   FLOWER   OF   A    DICOTYL. 


123 


PLATE  XVII.,  FIG.  1.— Upper  part  of  Flowering  Stem  of  Flax  (about  %  natural  size). 
FIG.  2.— Longitudinal  Section  of  one  of  the  Flowers  (somewhat  enlarged). 

FIG.  3.— A  Flower  with  the  Sepals  and  Petals  removed,  showing  andrrecium  and 
gyncecium :  a,  one  of  the  styles ;  b,  staminode  ;  c,  short  staminal  tube ;  d,  scars  left  by 
removal  of  floral  envelopes. 

FIG.  4.— Ground  Plan  of  Flower:  a,  sepal;  6,  petal;  c,  stamen;  d,  staminode;  e,  ovary 
in  cross-section. 


EXERCISE  XIV. 

STUDY  OF  THE  FLOWER  OF  A  KANUNCULACEOUS  PLANT. 

SELECTIONS  may  be  made  from  any  of  the  following :  Gold- 
thread (Coptis  trifolia,  Salisb.),  any  one  of  the  Buttercups  (as,  for 
example,  the  Common  Ranunculus  septentrionalis,  Poir.\  the 
Marsh  Marigold  (Caltha  palustris,  L.\  the  Columbine  (Aquilegia 
Canadensis,  L.\  the  Larkspur  (Delphinium  cousolida,  Z,.),  or  the 
Monkshood  (Acouitum  Napellus,  L.).  The  last  two  are  culti- 
vated in  gardens,  while  the  rest  are  all  common  native  plants. 

A  selection  is  made  of  the  Goldthread,  a  beautiful  little  plant 
exceedingly  common  in  the  bogs  of  our  northern  forests,  where  it 
grows  among  the  moss.  It  is  called  Goldthread  because  its  long, 
slender,  creeping  rhizomes,  not  more  than  a  millimetre  in  diam- 
eter, are  golden  yellow  in  color.  At  intervals  of  about  an  inch 
these  rhizomes  bear  minute  scales  occurring  alternately,  and  from 
near  these  issue  numerous  very  delicate  adventitious  roots,  also 
golden  yellow  in  color.  In  flowering-time,  which  occurs  in  May, 
two  long-petiolate,  exstipulate,  radical  leaves  may  be  observed, 
which  are  ternately  divided,  with  obovate-cuneate,  serrate,  and 
somewhat  trilobate  segments.  These  leaves  have  persisted  over 
winter,  and  are  smooth,  deep  glossy-green  above,  paler  below, 
and  lie  spread  out  upon  the  moss.  At  this  time  two  other  leaves, 
upright  and  in  the  process  of  unfolding,  are  also  to  be  seen,  and 
from  between  these  rises  the  slender  scape,  bracted  above  its  mid- 
dle and  terminated  by  a  single  white  flower. 

(1)  The  flower  is  studied  first  with  reference  to  its  parts.  Care- 
ful scrutiny  shows  that  there  are,  as  in  the  typical  flower  already 
studied,  four  kinds  of  floral  organs  :  an  outside  whorl,  imbricately 
arranged,  and  consisting  usually  of  five  distinct  pieces  (though  the 
number  varies  sometimes  to  six  or  seven);  a  second  whorl  of 
club-shaped  bodies,  each  hollow  and  with  a  small  aperture  at  the 
top ;  a  circle,  or  rather  several  circles,  of  distinct  stamens,  the 
number  varying  between  fifteen  and  twenty-five ;  and  in  the 

125 


126  LABORATORY    EXERCISES    IN    BOTANY. 

centre  a  whorl  of  pistils,  frequently  five  in  number,  but  often 
varying  from  three  to  seven. 

(2)  The  Calyx. — The  exterior  whorl,  from  its  color,  looks  like 
a  corolla,  but  is  really  to  be  regarded  as  a  calyx,  because  the 
whorl  of  club-shaped  bodies  next  interior  occupies  the  place  of 
the  corolla  and  must  be  regarded  as  such.     The  calyx  in  this  case 
illustrates  the  not  uncommon  fact  that  this  organ  may  become 
corolla-like,  and  take  the  place  of  a  corolla  in  its  function  of 
making  a  show  for  the  attraction  of  insects. 

(3)  The  corolla  in  this  flower  has  become  even  more  modified. 
It  is  no  longer  showy,  and,  as  has  been  seen,  its  petals  have  not 
the  usual  shape.     Indeed,  they  serve  an  altogether  different  func- 
tion from  the  ordinary  one ;  they  are,  in  fact,  nectaries,  or  repos- 
itories of  sweet  secretions.    The  change  from  the  ordinary  form  of 
a  petal  will  be  understood  better  if  a  comparison  be  made  of  these 
petals  with  those  of  a  true  Buttercup.     Figure  4  (PI.  XVIII.) 
represents  a  petal  of  Ranunculus  repens  with  a  nectary  at  its 
base.     One  may  easily  believe  that  the  Coptis,  a  close  relative  of 
the  Buttercup,  once  had   similar  petals,  and  that  these  in  time 
have  become  reduced  until  now  nothing  is  left  of  them  but  the 
nectary. 

(4)  The  Floral  Symmetry. — So  far,  however,  the  flower  con- 
1'nrms  very  well  to  the  dicotyl  pattern-flower  already  studied,  for 
the  two  whorls  are  each  usually  pentamerous  and  alternate  with 
each  other.     The  stamens,  though,  present  a  deviation  from  the 
type  which  is  almost  universal  in  the  Ranunculacese  and  which 
occurs  also  in  some  other  orders — namely,  they  are  indefinite  in 
number,  representing  perhaps  from  three  to  five  or  more  whorls. 
The  flower  is  unsymmetrical,  therefore,  as  respects  the  stamens. 

The  pistils,  while  showing  more  tendency  to  variation  in  num- 
ber than  either  sepals  or  petals,  may  still  be  regarded  as  conform- 
ing to  the  type,  since  not  infrequently  their  number  is  five,  and 
since,  as  in  the  other  members  of  this  order,  they  are  distinct 
from  each  other. 

(5)  Distinctness  of  Parts. — Another  characteristic  which    this 
flower  has  in  common  with  nearly  all  the  members  of  the  order 
to  which  it  belongs  is  the  absence  of  any  union  of  its  parts.     Not 
only  are  the  parts  of  the  same  whorl  all  distinct  or  separate  from 

other,  but  all  of  the  parts  are  separately  inserted  on  the 


STUDY  OF  THE  FLOWER  OF  A  RANUNCULACEOUS  PLANT.   127 

receptacle ;  that  is,  there  is  no  union  of  parts  belonging  to  dif- 
ferent whorls.  The  Columbine  and  a  few  other  members  of  the 
order  are  slightly  exceptional  in  the  fact  that  their  pistils  are 
partially  united  at  their  base. 

(6)  Studying  now  the  floral  organs  individually,  it  will  be  found 
that  the  sepals  are  short-stalked  or  clawed,  elliptic-lanceolate  in 
outline,  acutish  or  somewhat  obtuse  at  the  apex,  spreading  when 
the  flower  is  in  full  blossom,  and  each  five  or  six  millimetres  in 
length. 

The  petals  are  less  than  half  as  long,  and  somewhat  resemble 
large  stamens. 

The  stamens  have  filiform  stalks  or  filaments  and  two-lobed 
anthers.  The  base  of  each  anther  is  inserted  directly  on  the  end 
of  the  filament — a  position  which  is  described  as  innate — and 
each  lobe  opens  to  shed  its  pollen  by  means  of  a  longitudinal  slit 
on  the  side.  Since,  therefore,  the  anthers  face  neither  inward  nor 
outward,  they  are  described  as  lateral. 

Each  pistil  is  stalked  or  stipitate,  a  rather  unusual  thing  in  pis- 
tils, but  one  which  one  should  expect  would  occasionally  occur, 
since  a  pistil  is  derived  from  a  leaf.  There  is  a  short  style,  and  a 
relatively  long  recurved  stigma  which  is  stigmatic  along  its  ven- 
tral side  only. 

Making  a  cross-section  through  the  ovary,  it  will  be  found  that 
there  is  a  double  row  of  ovules  on  the  ventral  side,  as  shown  on 
Plate  XVIII.  (Fig.  3,  e).  The  pistil  is  in  fact  a  simple  one,  rep- 
resenting a  single  modified  leaf — a  leaf  so  rolled  up  that  its  ven- 
tral surface  and  its  edges  are  interior,  and  having  the  ovules 
borne  on  these  internal  edges,  which  thus  constitute  the  placenta. 

On  opening  one  of  the  pistils  lengthwise  the  small  ovules 
will  be  observed  arranged  very  much  as  are  peas  in  a  pod.  They 
are,  however,  individually  too  small  to  admit  of  the  structure 
being  studied  with  an  ordinary  magnifier. 


STUDY  OF  THE  FLOWER  OF  A  RANUNCULACEOUS  PLANT.  129 


PLATE  XVIII.,  FIG.  1.— Plant  of  Coptis  trifolia  (%  natural  size) :  a,  scales  at  base  of 
young  leaves  and  scape ;  6,  bract  on  scape  ;  c,  one  of  the  young  leaves. 

FIG.  2.— Ground  Plan  of  Flower. 

FIG.  3.— A  sepal,  a;  a  petal,  6;  a  stamen,  c;  a  pistil,  d;  and  the  cross-section  of  the 
ovary,  showing  placentation,  e. 

FIG.  4.— Petal  of  Buttercup,  showing  nectary,  a,  at  its  base. 
9 


EXERCISE  XY. 

STUDY  OF  A   DIMEROUS  FLOWER. 

ANY  of  the  following  plants  bear  flowers  that  may  be  studied 
to  advantage :  the  Bloodroot  (Sanguinaria  Canadensis,  Z.),  the 
Celandine  (Chelidonium  majus,  L.\  the  Poppy  (Papaver  som- 
niferum,  L.\  the  Prickly  Poppy  (Argemone  Mexicana,  L.\  the 
Climbing  Fumitory  (Adlumia  cirrhosa,  Rqf.),  the  Dutchman's 
Breeches  (Dicentra  cucullaria,  -DC.),  or  the  Pale  Corydalis  (Cory- 
dalis  glauca,  Pursh). 

For  this  study  the  first  in  the  list  is  chosen.  The  Bloodroot 
is  a  very  common  herb  found  in  rich  woods  throughout  the  North- 
eastern United  States  and  Canada.  Its  conspicuous  white  or  pink- 
ish blossoms  are  among  the  most  prized  of  our  early  spring  flow- 
ers, and  its  short,  thick  rhizomes  are  useful  in  medicine.  The 
whole  plant  contains  a  copious  orange-red  milk-juice  which  is 
very  acrid  to  the  taste,  and  the  color  of  which  has  given  origin 
both  to  the  common  and  to  the  first  part  of  the  scientific  name  of 
the  plant. 

I.  SUBTERRANEAN  PARTS. — The  rhizomes  are  reddish-tinged 
on  the  outside,  from  four  to  six  centimetres  in  length  and  from 
ten  to  twelve  millimetres  thick,  are  nearly  circular  in  cross-sec- 
tion, somewhat  enlarged  at  intervals  of  about  one  centimetre,  dis- 
tinctly annulate,  with  rather  faint  stem-scars  on  the  enlargements 
on  the  upper  surface,  and  provided  with  rather  numerous  nearly 
simple  adventitious  roots  that  spring  chiefly  from  the  sides  and 
lower  surface,  but  occasionally  also  from  the  upper.  The  rootlets 
have  the  same  color  as  the  rhizome,  and  are  from  one  to  one  and 
a  half  millimetres  in  thickness  at  their  base. 

The  rhizome,  when  mature,  sends  out  from  lateral  buds  from 
one  to  several  branches  which  are  relatively  thin  at  the  point  of 
attachment  to  the  main  body.  Not  infrequently  an  old  rhizome 
may  be  found  with  five  or  six  of  these  branches  attached  to  it, 
each  producing  a  leaf  or  leaves  and  a  flower-stalk.  Ultimately, 

131 


132  LABORATORY    EXERCISES   IN    BOTANY. 

though,  the  parent  rhizome  dies,  setting  the  branches  free,  so  that 
the  latter  become  independent  plants. 

A  cross-section  of  the  rhizome  shows  a  thin  cortex  and  a  verv 
thick  and  large-celled  pith,  and  these  are  separated  from  each 
other  by  a  narrow  circle  of  vasal  bundles.  The  rest  of  the  struc- 
ture is  destitute  of  Jignified  tissue,  and  even  the  bundles  con- 
tain but  little.  Pith  and  cortex  are  thickly  studded  with  secre- 
tion-cells which  contain  the  red  milk-juice  already  referred  to. 

At  the  end  of  the  rhizome  or  of  a  branch,  and  well  toward  the 
lower  side,  is  the  scaly  terminal  bud  from  which  spring  the  aerial 
stern  and  leaves.  At  the  base  of  this,  on  the  lower  side  and  in 
the  axil  of  one  of  the  lower  scales,  is  a  minute  bud  destined  to 
continue  the  growth  of  the  underground  stem. 

II.  ABOVE-GROUND  PARTS. — From  each  terminal  bud  there 
arises  in  early  spring  a  single  erect  leafless  stem  about  twelve 
centimetres  high  which  is  terminated  by  a  single  flower.  A  stem 
like  this,  which  bears  flowers  only,  is  called  a  scape.  The  lower 
bracts  of  the  bud  develop  but  slightly,  the  upper  ones  consider- 
ably, so  that  the  latter  rise  two  or  three  inches  above  the  soil. 
The  bud  contains  also  in  its  interior  usually  two  true  leaves,  one 
of  which  emerges  from  the  bud,  but  does  not  fully  unfold  at  the 
time  of  flowering,  while  the  other  does  not  make  its  appearance 
until  considerably  later. 

(1)  The  leaves  are  long-petiolate,  and,  since  they  spring  from 
underground  parts,  are  called  radical  leaves.     They  are  smooth 
and  glaucous  on  both  surfaces.     The  blades  are  nearly  orbicular, 
deeply  cordate  at  the  base,  and  palmately  lobate  on  the  margin. 
The  venation  forms  a  fine  example  of  palmate  reticulation,  the 
veins  being  quite  prominent  on  the  lower  surface. 

(2)  The  Flower. — In  order  to  get  a  complete  knowledge  of  the 
floral  structure  it  is  necessary  to  study  it  in  different  stages  of 
anthesis.     In  an  early  stage,  when  the  flower  first  emerges  from 
the  protection  of  the  convolute  leaf-blade,  the  two  greenish  sepals 
fall  away.     Sepals  or  other  foliar  organs  which  thus  early  disap- 
pear are  called  caducous.    The  petals  are  usually  eight,  but  some- 
times twelve,  sixteen,  or  even  more,  are  either  pure  white  or  tinged 
with  pink,  and  are  apparently  arranged  in  whorls  of  two.  tlie  outer 
and  broader  whorl  alternating  with  the  sepals,  the   next  pair  \\  ith 
the  first  pair  of  petals,  and  so  on.     The  sepals  are  oval  or  ovate 


STUDY   OF   A   DIMEROUS   FLOWER.  133 

in  outline  and  a  little  more  than  half  as  long  as  the  petals.  The 
outer  petals  are  lance-oval  or  lance-ovate,  obtuse,  and  about  three 
millimetres  in  length.  The  inner  petals  are  much  narrower  than 
the  outer  ones. 

The  stamens  are  numerous,  usually  from  sixteen  to  thirty-two, 
and  are  probably  to  be  regarded  as  being  arranged  in  successive 
whorls  of  two,  though  they  are  so  crowded  that  the  fact  is  not 
evident  from  inspection.  The  stamens  are  not  of  equal  length, 
the  inner  being  longer  than  the  outer. 

Each  stamen  consists  of  a  white  thread-like  stalk  or  filament 
and  an  oblong,  somewhat  curved,  two-lobed,  adnate,  and  extrorse 
anther  which  dehisces  longitudinally. 

Ail  the  parts  of  the  flower  thus  far  considered  are  distinct  from 
one  another  and  separately  inserted  on  the  convex  receptacle. 

The  pistil,  however,  consists  of  two  leaf-elements  or  carpels 
united.  This  is  shown  not  only  by  the  distinctly  two-lobed 
stigma  and  the  more  or  less  two-lobed  ovary,  but  by  the  internal 
structure,  presently  to  be  studied. 

Except  the  papillose  yellow  stigma,  the  pistil  is  glaucous  and 
green.  The  style  is  short  and  erect ;  the  ovary  is  somewhat  flat- 
tened, with  two  faint  ridges  running  from  base  to  stigma  along  its 
margins,  and  is  inserted  directly  on  the  top  of  the  receptacle. 

A  cross-section  reveals  the  fact  that  the  ovary  is  one-celled  and 
that  the  numerous  ovules  are  auatropous  and  arranged  in  two 
opposite  vertical  rows  on  the  ovary-walls.  That  is  to  say,  the 
placentation  is  marginal. 

Although  the  fact  that  the  ovules  are  anatropous  might  be  made 
out  with  an  ordinary  magnifying  glass,  it  can  more  easily  be  done 
later  on,  when  the  pistil  has  ripened,  or  nearly  so,  into  a  fruit. 

It  is  clear  from  our  study  that  the  numerical  plan  of  this  flower 
is  that  of  two  ;  it  is  therefore  dimerous.  All  the  different  organs 
of  a  flower  are  represented ;  it  is  therefore  complete.  All  the 
petals  are  distinct  or  un united  ;  the  flower  is  therefore  choripetal- 
ous.  And  the  stamens  are  not  attached  to  any  other  floral  organ, 
but  are  directly  inserted  upon  the  receptacle  below  the  pistil ;  they 
are  therefore  hypogynous. 

Drawings  should  now  be  made  showing  (1)  the  plant  as  a  whole 
when  in  the  blossoming  stage,  (2)  the  separated  parts  of  the  flower, 
and  (3)  a  ground  plan  of  the  flower. 


STUDY   OF   A   DIMEROUS   FLOWER. 


135 


c     d      e 


PLATE  XIX.,  FIG.  1.— Whole  Plant  of  Bloodroot  (natural  size) :  a,  rhizome  with  its 
ring-like  scars  and  rootlets ;  6,  one  of  the  lower  bud-scales ;  c,  imperfectly-developed 
leaf-blade  ;  d,  the  fully-expanded  flower,  the  calyx  having  fallen  away. 

FIG.  2.— Different  Parts  of  Flower  (%  natural  size) :  a,  sepal ;  &,  one  Of  the  outer  petals ; 
c,  one  of  the  inner  petals  ;  d,  two  of  the  stamens— the  one  to  the  left  an  outer  one,  and 
the  one  to  the  right  an  inner  one  ;  e,  pistil  viewed  from  different  directions. 

FIG.  3.— Ground  Plan  of  Flower. 


EXERCISE  XVI. 

STUDY   OF   A  CKUCIFEROUS  FLOWER 

ANY  one  of  the  following  plants  would  serve  the  purpose  well : 
Rock  Cress  (Arabis  lyrata,  L.),  Tooth  wort  (Dentaria  laciniata, 
Muhl.\  Spring  Cress  (Cardamine  rhomboidea,  DC.\  Horse  Radish 
(Nasturtium  Armoracia,  Fries),  Rocket  (Hesperis  matronalis,  jL), 
Charlock  or  Field  Mustard  (Brassica  Siuapistrum,  Boiss.\  or 
Black  Mustard  (Brassica  nigra,  Koch.}.  All  are  common  plants, 
and  some  one  of  them  may  be  found  in  blossom  in  any  portion 
of  the  growing  season. 

The  first  in  the  list  is  made  the  subject  of  the  present  study. 
Arabis  lyrata  is  a  not  uncommon  herb  in  sandy  or  light  soil,  and 
blossoms  in  early  spring.  It  grows  to  the  height  of  from  four  to 
eight  inches,  has  a  well-developed  tap-root,  a  rosette  of  radical 
leaves  which  are  lyrately  pinnatifid  and  spread  out  flat  upon  the 
ground,  a  stem  which  branches  more  or  less,  is  pubescent  below 
like  the  radical  leaves,  and  is  smooth  above,  bears  alternate,  entire, 
linear-lanceolate,  smooth  leaves,  and  terminal  or  sometimes  axil- 
lary racemes  of  white  flowers. 

(1)  Anthotaxy. — In  some  species  of  plants  the  flowers  occur 
singly,  either  at  the  end  of  the  stem  or  in  the  axils  of  ordinary 
leaves,  while  in  others  they  are  clustered,  and  among  flower  clus- 
ters there  is  a  great  variety.  The  arrangement  of  flowers,  includ- 
ing the  various  modes  of  clustering,  is  called  anthotaxy  ;  and,  since 
the  anthotaxy  is  usually  the  same  in  the  same  species  of  plant,  its 
study  is  of  importance  in  the  identification  of  species.  There  are 
two  principal  types  of  anthotaxy,  the  indeterminate  and  the  deter- 
minate,  and  there  are  several  varieties  of  each.  In  the  indeter- 
minate type  the  flowers  of  the  cluster  develop  in  succession  from 
the  base  of  the  floral  axis  toward  its  apex,  the  oldest  blossoms 
being  lowest  down  on  the  axis,  the  youngest  next  its  apex.  In 
the  determinate  type  the  arrangement  is  the  precise  reverse  of 

137 


138  LABORATORY    EXERCISES    IN    BOTANY. 

this ;  that  is  to  say,  the  unfolding  of  the  blossoms  takes  place 
from  the  apex  of  the  axis  toward  its  base,  and  the  oldest  flower 
is  at  the  apex.  If  the  clusters  are  compact,  and  particularly  if 
flat-topped,  the  flowering  in  the  first  type  will  proceed  from  the 
margin  toward  the  centre  of  the  cluster,  and  in  the  latter  from 
the  centre  toward  the  margin.  The  two  types  are  therefore  often 
called  centripetal  and  centrifugal  respectively. 

Inspecting  the  anthotaxy  of  Arabis,  it  will  be  found  that  the 
flowers  occur  in  succession  along  a  lengthened  axis,  the  oldest  at 
the  base.  The  cluster  is  therefore  indeterminate  or  centripetal. 
It  will  be  observed,  moreover,  that  the  floral  axis  is  lengthened 
and  that  the  individual  flowers  have  stalks  or  pedicels  of  their 
own.  This  is  therefore  the  kind  of  indeterminate  authotaxy  that 
is  called  a  raceme,  a  very  common  variety  of  flower  cluster.  A 
peculiarity  will  be  observed  in  this  raceme — namely,  there  are  no 
small  modified  leaves  or  bracts  at  the  base  of  the  pedicels,  as  is 
most  commonly  the  case  in  racemes.  The  racemes,  in  fact,  are 
bractless  almost  throughout  the  family  of  plants  to  which  this  one 
belongs.  Had  the  flowers  been  sessile  or  without  pedicels  on  the 
lengthened  axis,  the  cluster  would  have  been  called  a  spike;  had 
the  flowers  been  sessile  and  also  arranged  on  a  very  short  axis, 
the  cluster  would  have  been  called  a  head  ;  had  either  the  spike  or 
the  head  been  fleshy  and  subtended  by  a  conspicuous  and  more  or 
less  showy  bract  or  spathe,  the  cluster  would  have  been  called  a 
spadix ;  had  the  flowers  been  arranged  as  in  a  spike,  but  each 
subtended  by  a  scaly  bract,  the  cluster  would  have  been  called  a 
catkin  or  arnent ;  had  the  axis  been  somewhat  shortened  and  the 
lower  pedicels  lengthened  so  as  to  form  a  somewhat  flat-topped 
cluster,  it  would  have  been  called  a  corymb ;  and  had  the  axis 
been  reduced  almost  to  a  point  while  the  pedicels  remained  long, 
the  cluster  would  have  been  called  an  umbel.  Racemes,  spikes, 
corymbs,  and  umbels  may  also  be  more  or  less  branching,  and 
hence  called  compound. 

(2)  Numerical  Plan  and  Symmetry  of  the  Flower. — Inspection 
of  a  flower  of  Arabis  will  disclose  a  circle  of  four  small  greenish 
sepals,  all  distinct,  nearly  alike,  and  arranged  in  a  circle  ;  alternat- 
ing with  these,  four  much  larger,  distinct,  and  similar  white  petals; 
a  circle  of  six  distinct  stamens,  four  of  them  longer  than  the  other 
two ;  and  a  single  two-celled  and  clearly  two-carpeled  pistil.  The 


STUDY   OF    A   CRUCIFEROUS    FLOWER.  139 

two  outer  and  smaller  stamens  are  inserted  on  the  receptacle  slightly 
lower  down  than  the  other  four,  and  hence  one  may  conclude  that 
they  are  members  of  a  different  whorl.  The  four  inner  and  larger 
stamens  also  occur  in  pairs,  each  pair  occupying  the  interspace 
between  two  of  the  petals.  It  might  be  concluded  from  this, 
especially  as  in  some  species  of  the  family  the  filaments  of  each 
pair  are  found  united  at  the  base,  that  each  pair  is  formed  by  the 
division  or  branching  of  a  single  stamen.  Is,  then,  the  numerical 
plan  of  the  flower  that  of  two  or  that  of  four  ?  This  is  one  of 
the  botanical  questions  which  cannot  be  answered  offhand,  but 
which,  if  answered  at  all,  can  be  safely  done  only  by  the  most 
careful  study  of  the  floral  structure.  There  is  reason  to  believe, 
from  a  study  of  the  arrangement  of  the  woody  bundles  that  pass 
from  the  stem  into  the  respective  floral  organs,  that  the  flower 
originally  had  at  least  five  whorls — one  of  sepals,  one  of  petals, 
two  of  stamens,  and  one  of  pistils — and  that  the  number  in  each 
whorl  was  at  least  four,  or  even  probably  five.  It  is  reasonable  to 
suppose  that  changes  in  the  original  plan  have  been  brought  about 
by  the  visits  of  insects,  the  number  of  the  parts  of  the  flower  hav- 
ing thus  become  modified  and  reduced  to  the  present  limits. 

It  is  remarkable  that  throughout  the  family — which,  by  reason 
of  the  cross-shaped  appearance  of  the  flowers,  is  called  the  Cru- 
oiferas — there  should  be  such  a  close  resemblance  in  the  floral  struc- 
ture. Whenever  one  meets  with  a  four-sepaled  and  four-petaled 
flower  having  tetradynamous  (that  is  to  say,  two  short  and  four  long) 
stamens  and  a  two-celled  pistil,  all  separately  inserted  on  the  re- 
ceptacle, one  may  be  certain  that  the  plant  bearing  it  is  a  member 
of  the  natural  order  Cruciferse. 

(3)  Stamens  and  Pistil. — Examining  the  stamens  particularly, 
it  will  be  found  that  the  anthers  are  inserted  by  their  bases  directly 
on  the  ends  of  the  filaments.  The  anthers  are  therefore  called 
innate.  They  are  also  introrse,  or  face  inward  toward  the  pistil, 
and  they  dehisce  longitudinally. 

The  pistil  has  a  short  thick ish  style,  a  slightly  convex,  capi- 
tate stigma,  and  a  somewhat  flattened  ovary.  Making  a  trans- 
verse section  of  the  latter,  it  will  be  observed  that  it  is  two-celled, 
but  the  insertion  of  the  ovules  is  different  from  that  in  most 
plurilocular  ovaries — namely,  the  ovules  are  borne  at  the  junc- 
tion of  the  partition  with  the  walls,  and  not  in  the  centre  or  axis 


140  LABORATORY   EXERCISES  IN   BOTANY. 

of  the  ovary.      This  also  aids  in  distinguishing  the  Cruciferae 
from  other  plants. 

Let  the  student  now  study  and  make  drawings  of  the  flower  of 
some  other  cruciferous  plant. 


STUDY   OF   A    CRUCIFEROUS    FLOWER. 


141 


PLATE  XX.,  FIG.  1.— Arabis  lyrata,  entire  plant  (%  natural  size) :  a,  upper  flower-bud 
of  one  of  the  racemes;  &,  a  fully-opened  flower;  c,  an  older  flower  from  which  the 
petals  and  stamens  have  fallen ;  d,  one  of  the  cauline  leaves :  e,  one  of  the  radical 
leaves ;  /,  the  tap-root. 

FIG.  2.— Vertical  Section  of  one  of  the  Flowers  (enlarged),  showing  insertion  of  parts. 
FIG.  3.— Ground  Plan  of  Flower. 


EXEECISE  XVII. 

STUDY  OF   A  KOSACEOUS  FLOWER. 

SELECTIONS  may  be  made  from  the  following  common  plants : 
the  Strawberry  (Fragaria  Virgiuiaua,  Mitt.),  the  Cinquefoil 
(Potentilla  Canadensis,  L.\  the  Prairie  Rose  (Rosa  setigera, 
Mich-x.),  the  Smooth  Rose  (Rosa  blanda,  Ait.\  the  Dog  Rose 
(Rosa  canina,  L.\  the  Wild  Red  Plum  (Pruuus  Americana, 
Marshall),  the  Cultivated  Cherry  (Primus  avium,  L.),  the  Black- 
berry (Rubus  villosus,  Ait.\  and  the  Dewberry  (Rubus  Canaden- 
sis, L.). 

For  this  study  the  commonly  cultivated  Bird  Cherry  (Prunus 
avium)  is  selected. 

The  flowers  of  this  tree  spring  from  axillary  buds  of  the  pre- 
vious autumn,  and  occur  either  singly  or  in  umbel-like  clusters 
of  from  two  to  five,  as  shown  on  Plate  XXI.  (Fig.  1).  On  the 
same  twig  may  be  seen  the  leaf-buds  with  the  conduplicately-folded 
leaves  in  the  process  of  unfolding. 

(1)  The  flower  as  a.  whole  may  be  described  as  hermaphrodite, 
complete  and  regular,  but  not  wholly  symmetrical,  the  gynoecium, 
and  frequently  the  androecium,  deviating  more  or  less  from  sym- 
metry.    The  flower  being  showy  and  white,  perfumed,  and  pos- 
sessing adhesive  pollen,  the  conclusion  is  reached  that  it  is  ento- 
mophilous. 

(2)  The  calyx  may  be  regarded  as  gamosepalous  with  a  cup- 
shaped  tube  and  a  five-parted  limb.     It  is  so  regarded  by  many 
botanists,  but  others  view  the  cup  not  as  the  calyx-tube,  but  as  a 
hollow  receptacle  from  the  margin  of  which  spring  the  five  dis- 
tinct  sepals.      The    calyx-lobes  (or   sepals)  are  oblong,  obtuse, 
greenish,  and  valvately  arranged  in  the  bud. 

(3)  The  corolla  consists  of  five  somewhat  obcordate  or  nearly 
round,  white,  short-clawed,  spreading  petals,  about  fifteen  milli- 
metres long  and  inserted  on  the  throat  of  the  calyx  (or,  as  some 
view  it,  on  the  margin  of  the  receptacular  tube).     The  preflora- 

143 


144  LABORATORY    EXERCISES    IN   BOTANY. 

tion  of  the  corolla  is  quincuncial,  and  the  petals  when  expanded 
are  concave  on  their  upper  surface. 

(4)  The  andrcecium  consists  of  numerous  stamens  which,  like 
the  petals,  are  perigynously  inserted — that  is,  carried  up  above 
the  level  of  the  insertion  of  the  pistil  on  the  border  of  the  calyx- 
tube.     There  are  frequently  fifteen  or  twenty  stamens,  indicating 
the  presence  of  four  or  five  whorls  in  normal  flowers ;  but  in  this 
and  in  most  instances  where  the  stamens  are  numerous  their  num- 
ber also  varies,  and  it  is  common,  therefore,  to  describe  the  sta- 
mens in  this  and  similar  cases  as  indefinite. 

Each  stamen  consists  of  a  slender,  straight,  and  rather  rigid 
filament,  about  as  long  as,  or  a  little  longer  than,  the  petals,  and 
crowned  by  an  oval,  somewhat  versatile,  two-lobed,  two-celled, 
and  introrse  anther  which  dehisces  longitudinally. 

(5)  The  gyncecium  consists  of  a  single,  one-carpeled  pistil  which 
is  complete,  possessing  all  the  parts  of  a  pistil.    The  ovary  is  one- 
celled,  two-ovuled,  with  a  marginal  placentation  and  pendulous, 
anatropous  ovules.     The  style  is  erect  or  slightly  bent,  filiform, 
about  as  long  as  the  filaments,  and  bears  at  its  apex  a  slightly  con- 
cave and  somewhat  cordate  or  two-lobed  stigma. 

The  flowers  of  the  Rosacea3,  the  order  to  which  the  Cherry  be- 
longs, differ  among  themselves  in  many  minor  points,  as  in  antho- 
taxy,  color,  size,  number  of  stamens,  in  the  fact  that  the  pistils 
in  some  cases  are  distinct,  in  others  more  or  less  united,  in  the 
number  of  pistils,  and  even  in  the  adnation  of  the  calyx-tubes. 
As  respects  the  latter  point,  in  some  species  the  tube  grows  fast  to 
the  walls  of  the  ovary,  as  in  the  Apple,  for  example,  while  in 
others  it  remains  wholly  free,  as  in  the  Cherry  and  Peach.  The 
flowers  are  sometimes  even  diclinous  by  the  abortion  of  the 
stamens  in  some  specimens  and  the  pistils  in  others,  but  they  all 
agree  in  their  pentamerism  and  in  the  perigyny  of  the  petals  and 
stamens. 

In  appearance  the  flowers  of  the  RanunculaceaB  often  closely 
resemble  those  of  the  Rosaceae.  For  example,  one  of  the  Helle- 
bores, a  poisonous  ranunculaceous  plant,  is  so  nearly  like  a  Rose 
in  its  blossom  that  it  goes  by  the  common  name  of  "  Christ  mas 
Rose  ;"  and  what  young  botanist  has  not  mistaken  a  Potentilla 
for  a  Buttercup  ?  In  both  the  flowers  are  pentamerous  ;  in  both 
all  the  parts  are  distinct  or  ununited,  the  stamens  and  pistils  in- 


STUDY    OF    A    ROSACEOUS    FLOWER.  145 

definite,  and  the  flowers  yellow  with  spreading  corollas.  But  in 
the  Potentilla  the  stamens  and  petals  are  perigynous,  while  in  the 
Buttercup  they  are  hypogynous. 

This  illustrates  the  fact,  so  often  met  with  in  natural  history, 
that  structural  characters  are  vastly  more  important  in  determin- 
ing relationship  than  are  mere  superficial  resemblances.     In  fact, 
the  latter  are  often  very  misleading. 
10 


STUDY   OF   A    ROSACEOUS    FLOWER. 


147 


PLATE  XXI.,  FIG.  1.— Twig  of  Primus  avium,  L.  (%  natural  size). 

FIG.  2.— Ground  Plan  of  Cherry  Blossom. 

FIG.  3.— Vertical  Section  of  Cherry  Blossom,  showing  perigynous  corolla  and  stamens. 

FIG.  4.— Parts  of  Flower :  a,  one  of  the  petals  (%  natural  size) ;  6,  a  stamen  in  different 
views  ;  c  and  d,  different  views  of  the  stigma. 


EXERCISE  XVIII. 

STUDY  OF  A  PAPILIONACEOUS   FLO  WEE. 

THE  plants  of  the  very  numerous  sub-order  Papilionacea?  of  the 
natural  order  Leguminosse  all  have  papilionaceous  flowers.  Good 
ones  for  study  are  the  following :  the  Sweet  Pea  (Lathyrus  odora- 
tus,  Z.),  the  Scarlet  Runner  (Phaseolus  multiflorns,  Willd.\  the 
Marsh  Vetchling  (Lathyrus  palustris,  Z.),  the  Common  Pea 
(Pisura  sativum,  L.\  the  Wistaria  (Wistaria  sinensis,  DC.),  the 
Locust  (Robinia  Pseudacacia,  L.\  the  Lupine  (Lupinus  perenuis, 
Z.),  and  the  Broom  (Cytisus  scoparius,  Link}. 

The  first  of  these  is  selected  for  the  present  study. 

I.  EXTERNAL  CHARACTERISTICS. — (1)  Observe,  first,  that  the 
stem  differs  from  the  usual  form  of  stems  in  being  strongly  flat- 
tened or  wing-margined.    Its  surface,  like  that  of  the  other  parts, 
is  pubescent  and  somewhat  glandular.     It  is  herbaceous,  and  the 
plant  has  the  scandent  habit,  climbing  by  means  of  tendrils  which 
are  modified  leaflets  of  the  compound  leaf. 

(2)  The  leaves  are  alternate  and  stipulate,  with  ovate-lanceolate, 
acuminate,  half-sagittate  stipules  ;  the  petioles  are  wing-margined, 
and  the  blade  consists  of  a  single  pair  of  ovate-lanceolate,  entire, 
or  slightly  wavy-margined  leaflets  and  of  from  three  to  five  others 
developed  into  tendrils. 

(3)  The  showy,  sweet-scented  flowers  occur  in  long-ped uncled, 
few-flowered  racemes,  with  only  two  or  three  flowers  in  a  cluster, 
or  they  are  sometimes  solitary.     They  occur  in  the  axils  of  the 
upper  leaves. 

(4)  Draw  a  portion  of  the  plant,  about  six  or  eight  inches  of 
its  upper  end,  and  point  out  the  stem,  a  stipule,  a  petiole,  a  ten- 
dril, an  unopened  flower-bud,  and  a  fully-expanded  flower. 

II.  STRUCTURE  OF  THE  FLOWER. — (1)  Irregularity. — One  of 
the  most  striking  things  about  the  flower  is  the  irregularity  in  its 
shape.     From  a  fancied   resemblance  to  a  butterfly,  it  has  been 
called  papilionaceous.     Like  most  irregular  flowers,  it  faces  later- 

149 


150  LABORATORY    EXERCISES   IN    BOTANY. 

ally  or  to  one  side,  and  not  vertically.  Various  of  its  parts  are 
more  or  less  irregular.  The  gamosepalous,  five-toothed,  some- 
what campanulate  calyx  shows  irregularity  in  the  fact  that  it  has 
a  one-sided  insertion  on  the  receptacle,  and  also  in  the  fact  that 
the  upper  teeth  are  somewhat  shorter  than  the  other  three,  the 
lower  segment  being  longest  of  all. 

The  corolla  is  still  more  irregular  both  in  the  relative  size  and 
in  the  shape  of  its  parts.  While  the  calyx-lobes  are  somewhat 
irregular,  they  are  still  so  nearly  alike  in  size  that  they  are  found 
quite  regularly  imbricate  in  the  bud ;  but  the  petals  even  in  the 
bud  show  that  peculiar  kind  of  irregularly  imbricate  aestivation 
which  is  called  vexillary  and  which  is  indicated  in  the  ground  plan 
on  Plate  XXII.  (Fig.  4).  Examining  the  petals  of  the  fully- 
opened  flower,  the  upper  one  is  found  much  larger  and  more 
showy  than  the  rest.  It  is  called  the  vexillum,  or  standard.  The 
two  lateral  ones,  similar  to  each  other,  but  different  from  the 
rest,  are  called  alee,  or  wings,  and  the  two  lower,  partially  united 
to  form  an  organ  which  resembles  the  keel  of  a  boat,  have  hence 
been  called  the  carina,  or  keel. 

The  stamens  also  show  some  irregularities.  These  organs  are 
ten  in  number,  originally,  probably,  in  two  whorls  of  five  each, 
but  now  appearing  as  one.  Nine  of  them  are  somewhat  unequally 
united  by  their  filaments  for  more  than  half  their  length,  while 
the  other  one,  the  upper  one  in  the  ordinary  position  of  the 
flower,  is  distinct.  They  are  also  somewhat  unequal  in  length. 

The  simple  pistil  is  also  slightly  irregular  in  the  fact  that  the 
style  is  bent  abruptly  upward  near  its  origin.  It  is  also  bearded 
along  the  inner  side  only. 

(2)  Dissymmetry. — The  numerical  plan  of  the  flower  is  clearly 
that  of  five,  the  calyx  and  corolla  agreeing  with  this  number  and 
the  stamens  being  a  multiple  of  it.     Moreover,  the  petals  alter- 
nate with  the  teeth  of  the  calyx,  and,  as  has  been  seen,  the  sta- 
mens are  probably  to  be  regarded  as  in  two  alternating  whorls  of 
five  each.     So  far,  therefore,  the  flower  is  symmetrical.     But  in 
the  pistil  is  found  a  deviation,  for  there  is  but  one  instead  of  tin- 
expected  number  five. 

(3)  Cohesion. — It  has  already  been  observed  that  the  calyx   is 
gamoeepalon?,  the  two  sepals  being  united  for  about  one-half  their 
length.     The  corolla  is  regarded  as  choripetalous,  since  the  petals 


STUDY   OF   A    PAPILIONACEOUS    FLOWER.  151 

are  distinct  at  the  base,  though  those  forming  the  keel  are  united 
toward  the  apex.  The  stamens — forming  as  they  do  two  groups 
by  the  union  of  the  filaments  of  nine  of  them,  while  the  other  one 
remains  distinct — are  described  as  diadelphous. 

Since  the  flower  is  on  the  numerical  plan  of  five,  one  would 
naturally  expect  to  find  either  five  distinct  pistils  or  else  one  com- 
pound pistil  composed  of  five  united  carpels.  Is  the  one  pistil 
which  is  present  one-carpeled  or  five-carpeled  ?  This  question 
can  be  answered  only  by  studying  the  structure.  Observing  the 
stigma,  it  will  be  found  to  be  entire,  and  not  at  all  lobed  or  divided. 
This  is  evidence,  so  far  as  it  goes,  of  a  one-carpeled  pistil.  But 
there  must  be  additional  proof.  Making  a  cross-section  of  the 
ovary,  this  is  found  to  be  only  one-celled,  and,  what  is  more  to 
the  point,  it  is  seen  that  the  ovules  form  a  double  row  along  the 
upper  or  ventral  side  of  the  ovary  only.  Had  there  been  two 
double  rows  on  opposite  sides,  one  would  have  been  obliged  to  re- 
gard the  pistil  as  two-carpeled,  or,  if  three,  three-carpeled,  and 
so  on ;  but,  since  there  is  only  one,  it  must  be  concluded  that  it  is 
but  one-carpeled,  or  represents  but  a  single  modified  leaf.  The 
flower  has  become  unsymmetrical,  then,  by  the  loss  of  four  of  its 
pistils. 

(4)  Adhesion. — Making  a  vertical  section  centrally  through  the 
flower  from  base  to  apex,  it  will  be  found  that  the  different  whorls 
of  floral  organs  are  successively  inserted  on  the  receptacle ;  there 
is  no  growing  of  one  floral  leaf  to  another  of  a  different  kind,  and 
therefore  no  adhesion  nor  adnation. 

(5)  Make  a  drawing  of  the  separated  petals,  so  that  their  rela- 
tive shapes  and  position  may  be  seen  at  a  glance.     Point  out  the 
vexillum,  one  of  the  alse,  and  one  of  the  two  petals  forming  the 
car  in  a. 

(6)  Draw  a  vertical  section  of  the  flower,  showing  the  succes- 
sion and  mode  of  insertion  of  the  parts.     Point  out  the  calyx, 
the  vexillum,  one  of  the  alse,  a  petal  of  the  carina,  the  staminal 
tube,  and  the  pistil. 

(7)  Draw  a  diagram  of  the  ground  plan  of  the  flower,  and 
point  out  the  following  parts :  a  sepal,  the  vexillum,  an  ala,  a 
petal  of  the  carina,  a  stamen,  and  the  pistil. 

(8)  Significance  of  the  Peculiarities  of  Structure. — The  showi- 
ness  of  the  flower,  its  agreeable,  odor,  and  the  fact  that  it  secretes 


152  LABORATORY    EXERCISES    IN    BOTANY. 

nectar  at  the  base  of  its  corolla  lead  one  to  suspect  that  the  plant 
makes  use  of  insects,  at  least  occasionally,  to  secure  cross-fertil- 
ization. The  irregularities  in  the  floral  structure  are  also  to  be 
regarded  as  adaptations  to  the  same  end.  The  large  upper  petal 
— and,  to  a  less  extent,  the  two  lateral  ones — are  specialized  for 
show.  That  the  flower  faces  laterally  instead  of  vertically  is 
explained  by  the  fact  that  thus  the  visiting  insect  is  more  liable 
t«»  alight  on  the  flower  in  such  a  way  as  to  touch  the  stigma  and 
also  to  become  dusted  with  the  pollen. 

Let  us  see  what  occurs  when  some  large  hymenopterous  insect, 
such  as  a  bumble-bee,  for  example,  visits  the  flower.  The  hori- 
zontally projecting  keel  and  wings,  particularly  the  former,  afford 
the  bee  a  most  convenient  landing-place.  The  stamens,  it  should 
be  borne  in  mind,  have  two-lobed,  introrse,  longitudinally  dehis- 
cent anthers,  which  in  the  undisturbed  flower  lie  in  close  contact 
with  the  upturned  portion  of  the  style,  immediately  beneath  the 
stigma,  and  the  stamens  are  all  enclosed  and  concealed  from  view 
by  the  keel.  The  upper  eud  of  the  style  is  rigid  like  the  rest  of  the 
pistil,  and,  as  has  been  seen,  its  front  side  is  covered  with  numerous 
stiff  hairs  which  form  a  kind  of  brush.  The  petals  composing 
the  keel  are  united  along  the  lower  edges  except  at  the  very 
base,  but  not  on  the  upper  side.  Being  thin  and  flexible  at  the 
base,  if  the  heavy  insect  alight  upon  the  keel,  the  latter  will  bend 
downward,  and  as  a  consequence  the  stigma  and  upper  end  of  the 
style  will  protrude  from  the  slit  in  the  upper  side.  The  anthers, 
however,  being  borne  upon  weak  filaments,  will  be  retained  within 
the  keel,  while  the  downward  movement  of  the  latter  will  cause 
the  hairy  style  to  brush  out  a  portion  of  the  adhesive  pollen  from 
the  anthers.  This,  or  a  part  of  it,  will  be  carried  against  the 
insect's  body.  The  stigma  will  also  necessarily  be  brought  into 
contact  with  the  insect's  body,  and  if  this  has  previously  been 
dusted  with  pollen  from  another  flower,  some  of  it  will  .almost 
certainly  be  deposited  upon  the  stigma.  The  protrusion  of  the 
stigma  and  the  brushing  out  of  the  pollen  may  easily  be  demon- 
strated by  simply  pressing  gently  downward  on  the  keel  with  the 
thumb  and  Ibivi'mger. 

Occasionally,  at  least,  cross-fertilization  is  thus  likely  to  be 
brought  about,  and  in  the  native  country  of  the  plant  probably 
habitually  so,  by  certain  large  hymenopterous  insects.  In  this 


STUDY    OF    A    PAPILIONACEOUS    FLOWER.  153 

country,  however,  and  in  England  cross-fertilization  by  insect 
agency  seems  to  be  a  rare  occurrence,  owing  probably  to  the  lack 
of  perfect  adaptation  of  the  flowers  and  native  insects  to  each 
other.  The  flowers,  though,  are  self-fertilized  and  seed  freely. 
It  is  evident  that  they  are  so  constructed  that  in  case  of  failure 
to  receive  other  pollen  they  can  utilize  their  own.  That  Nature 
did  not  form  them,  however,  for  habitual  self-fertilization  is 
clearly  indicated  not  only  by  the  structure  of  the  flower  as  ex- 
plained above,  but  also  by  the  fact,  observed  by  Mr.  Darwin,  that 
the  seeds  produced  by  cross- fertilization  develop  stronger  and 
more  vigorous  plants  than  those  produced  by  self-fertilization. 

The  student  should  now  study,  describe,  and  draw  one  of  the 
other  PapilionaceaB  mentioned  at  the  beginning  of  this  exercise. 


STUDY   OF    A    PAPILIONACEOUS    FLOWER. 


155 


9 
h 


a 


PLATE  XXII.,  FIG.  1.— Drawing  of  Upper  Part  of  Plant  of  Lathyrus  odoratus  (% 
natural  size) :  a,  winged  stem  :  b,  stipule  ;  c,  flattened  or  alate  petiole  ;  d,  a  leaflet-tendril ; 
e,  flower-bud,  one  of  a  cluster  of  three;  /,  vexillum,  or  large  upper  petal  of  corolla;  g, 
one  of  the  alse  or  wings ;  h,  earina  or  keel. 

FIG.  2.— The  Petals  of  the  Corolla  separated  so  as  to  show  their  shapes:  a,  vexillum  ; 
6,  ala ;  c,  one  of  the  petals  of  the  carina. 

FIG.  3.— Vertical  Section  of  one  of  the  Flowers,  showing  insertion  of  parts :  a,  vexil- 
lum  ;  b,  ala  ;  c,  stamens  ;  d,  carina  ;  e,  staminal  sheath  ;  /,  ovary  :  (j,  calyx-tooth. 

FIG.  4.— Diagram  of  Ground  Plan  of  Flower  :  a,  sepal ;  6,  vexillum  ;  c,  ala  ;  d,  stamen  ; 
•e,  petal  of  carina  ;  /,  pistil. 


EXERCISE  XIX. 

FLOWER  OF  A   GAMOPETALOUS   DICOTYL. 

SELECTIONS  may  be  made  from  the  following :  the  Jamestown 
Weed  (Datura  Stramonium,  L.),  the  Common  Potato  (Solanum 
tuberosum,  L.),  the  Ground  Cherry  (Physalis  pubescens,  Z.),  the 
Common  Morning-glory  (Ipornea  purpurea,  Lam.\  the  Hedge 
Bindweed  (Convolvulus  sepium,  L.),  the  Lungwort  (Mertensia  Vir- 
ginica,  DC.),  the  Wild  Phlox  (Phlox  divaricata,  L.),  the  Fringed 
Gentian  (Gentiana  crinita,  Frod.\  the  Harebell  (Campanula  rotun- 
difolia,  L.\  the  Partridge  Berry  (Mitchella  repens,  L.),  and  the 
Bluets  (Houstonia  caerulea,  L.). 

The  last  mentioned  on  this  list  is  selected  for  the  present  study. 
The  Houstonia  is  a  beautiful  little  plant,  abundant  in  open  and 
moist  ground  in  most  parts  of  the  Northern  United  States,  where 
it  blossoms  in  early  spring.  Humble  and  unpretentious  as  it  is, 
it  is  a  member  of  the  same  family  of  plants  as  that  to  which  the 
Coifee  and  Cinchona  trees  belong — the  natural  order  Rubiacese. 
The  delicate  stems  are  somewhat  branching,  more  or  less  quad- 
rangular, erect,  and  rise  to  the  height  of  from  three  to  five 
inches.  They  spring  from  slender,  filiform  rhizomes  which  give 
rise  to  even  more  slender  fibrous  rootlets.  The  small,  spatulate- 
oblong  radical  leaves  are  petiolate  and  entire  or  somewhat  toothed. 
The  opposite  stem-leaves  are  smaller  and  narrower,  the  upper  ones 
being  reduced  to  linear  bracts,  and  the  bases  are  connected  by 
minute  entire  stipules.  The  flowers  are  solitary  at  the  ends  of  the 
main  stem  and  its  branches. 

(1)  The  calyx  is  gamosepalous,  its  tube  adherent  to  the  walls  of 
the  ovary,  and  its  limb  separated  into  four  small,  linear,  at  first 
erect  or  ascending,  but  afterward  spreading  lobes,  which  are  green 
and  persistent. 

(2)  The  corolla  is  gamopetalous  and  hypocrateriform,  with  a 
tube  from  five  to  seven  millimetres  long,  narrow  below  and  larger 
above.     The  flowers  are  of  two  forms — one  with  the  enlargement 

157 


158  LABORATORY    EXERCISES    IN    BOTANY. 

beginning  about  the  middle  of  the  tube  and  extending  to  the 
throat,  the  other  with  the  enlargement  beginning  higher  up.  The 
color  of  the  tube  is  whitish  or  yellowish.  The  limb  is  pale  lilac 
or  sometimes  nearly  white,  and  is  parted  into  four  elliptical  seg- 
ments. The  throat  is  yellow. 

(3)  The  andrcedum  consists  of  four  stamens  borne  upon  the 
tube  of  the  corolla  and  nearly  sessile. 

The  anthers  are  introrse,  bilocular,  distinct,  alternating  with 
the  lobes  of  the  corolla,  and  longitudinally  dehiscent.  In  the 
two  forms  of  the  corolla  they  are  inserted  on  the  tube  at  different 
levels — in  one  near  its  middle,  in  the  other  in  the  throat. 

(4)  The  gyncecium  consists  of  a  single  bicarpellary  pistil  corn- 
posed  of  an  ovary  nearly  enveloped  in  the  calyx-tube,  and  a  slen- 
der, filiform  style  which  in  the  two  different  forms  differs  in  length. 
In  that  with  the  stamens  inserted  near  the  middle  of  the  tube  it 
rises  to  the  throat,  in  the  other  only  to  about  the  middle  of  the 
tube ;  that  is,  the  long-stamened  form  has  short  styles,  and  the 
short-stamened  one  has  long  styles. 

The  stigmas  are  two-lobed,  and  the  ovary  is  two-celled,  with 
axile  placentation  and  several  ovules  in  each  cell. 

(5)  Mode  of  Cross-fertilization. — The  question  naturally  arises  in 
the  thinking  mind,  why  flowers  of  two  different  forms  exist  within 
the  limits  of  the  same  species,  as  they  do  in  this  and  in  many  other 
plants.     Darwin  proved  this  arrangement  to  be  a  provision  to  en- 
sure cross-fertilization  by  insect  agency.    Suppose  an  insect,  whose 
beak  or  proboscis  is  just  long  enough  to  reach  the  nectar  in  the  bot- 
tom of  the  corolla,  to  visit  one  of  the  long-styled  flowers  of  this 
species :  the  insect's  throat  will  be  brought  into  contact  with  the 
stigmas,  and  the  middle  portion  of  its  proboscis  will  be  dusted 
with   the  adhesive  pollen   from  the  iutrorse  anthers,   which  so 
nearly  close  the  tube  at  the  level  of  their  insertion  that  the  nec- 
tar cannot  be  reached  without  contact  with  them.     The"  same 
thing  will  occur,  of  course,  if  the  insect  visits  other  flowers  of 
the  same  form,  but  none  of  the  pollen  thus  withdrawn  will  neces- 
sarily be  deposited  upon  the  stigmas.     But  when  the  insect  flies 
away  to  flowers  of  the  other  form  the  case  is  different.     Here  the 
anthers  are  so  situated  as  to  dust  the  insect's  throat  with  pollen, 
while  the  middle  part  of  its  proboscis  is  brought  into  contact  witli 
the  stigmas,  dusting  them  with  pollen  from  the  long-styled  flowers. 


FLOWER   OF    A    GAMOPETALOUS    DICOTYL.  159 

Thus  the  flower  attracts  insects  by  its  showy  color,  rewards 
them  for  their  visits  by  the  nectar  it  secretes,  and,  by  the  struc- 
ture of  its  corolla-tube,  together  with  the  proper  relative  adjust- 
ment of  the  anthers  and  styles,  makes  use  of  them  to  convey  the 
pollen  from  the  stamens  of  one  plant  to  the  stigmas  of  another, 
and  so  secures  cross-fertilization.  It  is  more  than  probable,  also, 
that  the  plant,  like  many  other  species  with  dimorphous  flowers, 
prefers  pollen  from  another  flower  to  its  own,  and  only  makes  use 
of  the  latter  when  that  from  a  flower  of  the  other  form  cannot  be 
obtained. 

The  Bouvardia  of  our  greenhouses,  a  related  plant  from  Mex- 
ico, is  often  available  for  study  when  Houstonia  is  not  in  blossom. 
The  flowers  are  also  dimorphous,  and  have  a  structure  quite  simi- 
lar to  that  of  Houstonia.  A  twig  with  ground  plan  and  vertical 
section  of  a  flower  is  shown  on  Plate  XXIII.  (Figs.  4,  5,  6). 


FLOWER   OF   A   GAMOPETALOUS    DICOTYL. 


161 


6 

PLATE  XXIII.,  FIG.  1.— Plant  of  Houstonia  cserulea  (about  %  natural  size). 

FIG.  2.— A  Long-styled  Flower  of  Houstonia  cut  vertically  to  show  structure :  st ,  stigmas ; 
an,  anthers  ;  ov,  ovary. 

FIG.  3.— Vertical  Section  of  Short-styled  Form  of  Houstonia,  to  show  internal  structure : 
an,  anther  ;  st,  stigmas  ;  ov,  ovary. 

FIG.  4.— Twig  of  Bouvardia,  bearing  a  cluster  of  three  salver-shaped  flowers :  a,  stipule. 
(%  natural  size.) 

FIG.  5.— Vertical  Section  of  one  of  the  Short-styled  Flowers  of  Bouvardia:  a,  corolla- 
lobe  ;  b,  stamen  ;  c,  corolla-tube  ;  d,  stigmas  ;  e,  style  ;  /,  calyx-lobe  ;  g,  ovary  ;  h,  peduncle. 

FIG.  6.— Ground  Plan  of  Bouvardia  Flower :  a,  sepal;  b,  petal;  c,  stamen;  rf,  ovary. 
11 


EXERCISE   XX. 

STUDY  OF  AN  ERICACEOUS  FLOWER 

SELECTIONS  may  be  made  from  the  following  plants  :  the  Com- 
mon Blueberry  (Vaccinium  corymbosum,  L.\  the  Stagger  Bush 
(Andromeda  mariana,  L.\  the  Leucothoe  (Leucothoe  racemosa, 
Gray),  the  Leather  Leaf  (Cassandra  calyculata,  Don),  the  Moun- 
tain Laurel  (Kalmia  latifolia,  L.),  the  Piuxter-flower  (.Rhododen- 
dron uudiflorum,  Torr.),  the  Prince's  Pine  (Chirnaphila  umbellata, 
Nutt.),  the  Shin-leaf  (Pyrola  elliptica,  Nutt.\  the  Wintergreen 
(Gaultheria  procumbens,  L.\  the  Bearberry  (A  rctostaphylos  uva- 
ursi,  Spreng.),  and  the  Trailing  Arbutus  (Epigsea  repens,  L.). 

From  this  list,  for  the  present  study,  choice  is  made  of  the 
Trailing  Arbutus.  This  exquisite  little  plant,  everywhere  a  favor- 
ite with  lovers  of  flowers,  has  a  wide  distribution  over  the  eastern 
part  of  North  America,  being  especially  abundant,  however,  in 
the  Alleghenies  and  in  the  rugged  pine  and  fir-clad  regions  bor- 
dering the  Great  Lakes  and  the  St.  Lawrence  River.  It  blooms 
among  the  earliest  of  our  spring  flowers,  often  sending  up  its 
fragrant  white-  or  rose-colored  blossoms  in  close  proximity  to  the 
lingering  snow-drifts  in  our  northern  woods.  Its  shrubby  stems 
are  slender,  extensively  trailing,  and  covered,  as  are  the  petioles 
and  inferior  leaf-surfaces,  with  rusty-brown  hairs.  The  leaves 
are  five  or  six  centimetres  long,  alternate,  evergreen,  with  slender 
and  rather  long-petiolate,  elliptical,  entire-margined,  prominently 
reticulate  blades  which  are  rounded  or  cordate  at  the  base  and 
rnucronate  at  the  apex. 

(1)  The  flowers  occur  in  short,  almost  spike-like  racemes  at  the 
ends  of  the  stems,  and  are  white    or   rose-tinged  and  attain  a 
length  of  one  and  one-half,  and  sometimes  even  two,  centimetres. 
The  pedicels  are  short,  two  or  three  millimetres  long,  and  brown- 
hairy,  as  are  also  the  scaly  bracts. 

(2)  The  calyx  is  five-parted  or  with  almost  distinct  sepals  which 

163 


164  LABORATORY    EXERCISES    IN    BOTANY. 

are  lanceolate,  entire,  nearly  smooth,  about  the  length  of  the  corolla- 
tube,  pointed,  and  scale-like. 

(3)  The  corolla  is  hypocrateriform,  the  lobes  of  its  five-parted 
limb  alternate  with  the  segments  of  the  calyx,  it  is  hypogynous, 
and  the  tube  is  hairy  on  the  interior.    In  some  the  color  is  white, 
in  others  deep-rose,  and  between  them  there  is  every  intermediate 
shade.     The  lobes  are  ovate,  entire,  obtuse,  or  mucronate. 

(4)  The  androscium  consists  of  ten  stamens  apparently  in  a  sin- 
gle whorl,  but  condensed  probably  from  two. 

According  to  Prof.  W.  P.  Wilson,  who  has  studied  these  flow- 
ers carefully,  the  plant  is  really  dioecious,  though  most  of  its 
flowers  still  possess  both  stamens  and  pistils.  In  the  pistillate 
flowers,  which  are  usually  rose-colored  and  smaller  than  the 
staminate  white  ones,  sometimes  the  stamens  have  wholly  dis- 
appeared ;  in  others  they  are  present,  but  in  a  very  abortive  con- 
dition ;  in  still  others  they  are  nearly  perfect  in  form,  but  still 
functionless.  Moreover,  the  stamens  in  the  male  flowers  are  not 
all  alike.  In  some  flowers  they  are  short,  in  others  long,  in  others 
still  of  intermediate  length,  and  a  corresponding  difference  is  found 
in  the  length  of  the  styles.  The  history  of  the  flower,  then,  may 
be  summed  up  as  follows :  It  was  first  hermaphrodite,  and  pos- 
sessed stamens  in  two  whorls  of  five  each,  and  the  stamens  of  the 
same  wht)rl,  at  least,  were  of  the  same  length  in  different  flowers. 
It  then  adapted  itself  to  cross-fertilization  by  insect  agency  by 
becoming  dimorphous  and  later  on  trimorphous,  and  perhaps 
polymorphous,  and  finally  the  stamens  in  some  flowers  and  the 
stigmas  in  others  became  abortive,  and  it  thus  reached  its  pres- 
ent dioecious  condition.  It  is  probably  onlv  a  question  of  time 
when  the  last  vestige  of  stamens  will  disappear  from  the  pistil- 
late- flowers,  and  of  pistils  from  the  staminate  ones — a  condition 
which  is  found  really  existing  in  many  other  flowers  at  the  present 
time. 

Observing  the  individual  stamens,  they  are  found  to  be  inserted 
at  the  base  of  the  corolla  on  the  receptacle — a  noteworthy  fact  in 
the  Heath  family,  as  in  most  other  flowers  with  gamopetalous 
corollas  the  stamens  are  inserted  on  the  corolla-tube. 

Tin-  filaments  are  bearded  at  the  base  and  attenuated  toward 
the  ajx-x. 

The  oblong  anthers  are  versatile,  iutrorse,  two-celled,  and  dil- 


STUDY   OF   AN    ERICA CEOUS   FLOWER.  165 

fer  from  those  of  most  other  Heaths  in  dehiscing  by  longitudinal 
slits  rather  than  by  pores  at  the  apex  of  the  lobes. 

The  pollen-grains  also  differ  from  those  of  most  plants  outside 
this  natural  order  in  being  composed  of  a  group  of  four  cells,  as 
shown  on  Plate  XXIV.  (Fig.  5,  a  and  b). 

(5)  The  gyncecium  consists  of  a  single  pistil,  but  it  is  com- 
pound, and  shows  by  its  structure  that  it  is  composed  of  five 
carpels.  It  thus  conforms  to  the  numerical  plan  of  the  flower, 
which,  except  in  those  unusual  specimens  in  which  the  stamens 
are  completely  aborted,  is  that  of  the  typical  dicotyl  already 
described. 

The  ovary  in  its  lower  part  is  faintly  ten-lobed,  but  these  lobes 
are  in  pairs.  The  upper  part  is  densely  hairy.  The  erect,  rather 
stout  cylindrical  style  is  crowned  with  a  five-lobed  stigma  which 
in  the  pistillate  flower  is  star-shaped  when  fully  expanded,  but  in 
the  staminate  one  never  opens. 

A  cross-section  of  the  ovary  shows  five  loculi,  an  axile  placen- 
tation,  and  numerous  small  anatropous  ovules. 


STUDY   OF   AN   ERTCACEOUS    FLOWER. 


167 


6 


PLATE  XXIV.,  FIG.  1.— A  Branch  of  Trailing  Arbutus  (%  natural  size). 
FIG.  2.— One  of  the  Staminate  Flowers  in  longitudinal  section  (slightly  enlarged). 
FIG.  3.— One  of  the  Stamens  (magnified  8  diameters). 
FIG.  4.— Pistil  (magnified  4  diameters). 

FIG.  5.— Pollen-grains  in  clusters  of  four  (magnified  200  diameters). 
FIG.  6.— Ground  Plan  of  Flower,  showing  imbricate  calyx  and  corolla. 
FIG.  7.— Cross-section  of  Ovary,  showing  its  ten  lobes  in  five  pairs,  its  five  loculi,  axile 
placentation,  and  numerous  ovules.    (Magnified  8  diameters.) 


EXEECISE  XXI. 

STUDY  OF  A  FLOWER  OF  THE  COMPOSITE. 

THE  following  species  of  this  natural  order  are  suitable  ones 
for  study  by  beginners :  the  Common  Sunflower  (Heliauthus 
animus,  L.),  the  Jerusalem  Artichoke  (Helianthus  tuberosus,  L.\ 
the  Common  Beggar-ticks  (Bidens  frondosa,  L.),  the  Sneeze-weed 
(Helenium  autumnale,  L.\  the  Ox-eye  Daisy  (Chrysanthemum 
Leucauthemum,  L.),  the  Burdock  (Arctium  Lappa,  L.\  the  Rattle- 
snake Weed  (Hieracium  venosurn,  L.)9  the  Dandelion  (Taraxacum 
officinale,  Weber),  and  Chicory  (Cichoriurn  Intybus,  L.). 

For  the  purpose  of  this  exercise  a  selection  is  made  of  the  Ox- 
eye  Daisy,  an  introduced  plant  now  become  exceedingly  common 
in  most  portions  of  the  Eastern  United  States,  where  ic  is  re- 
garded by  the  farmers  as  a  pernicious  weed.  Besides  the  common 
name  above  given,  it  is  also  called  in  different  localities  the  Mar- 
guerite, White  Daisy,  and  White  Weed. 

It  is  a  perennial  herb  with  ascending,  often  diffuse,  somewhat 
striate  and  smooth,  branching  stems  arising  from  short  rhizomes. 
The  lower  leaves  are  rounded,  oval,  or  spatulate,  and  taper  into 
rather  long  petioles,  and  are  coarsely  toothed,  incised,  or  lobed  on 
their  margins  ;  the  upper  leaves  are  oblauceolate,  lanceolate,  or 
linear-lanceolate,  and  pinnatifid.  They  are  smooth  and  deep-green 
both  above  and  below. 

(1)  The  anthotaxy  in  all  the  natural  order  Composite  is  inde- 
terminate, and  the   flower  clusters  consist  of   heads.     In  many 
species,  however,  the  heads  are  cymosely  arranged.     In  this  spe- 
cies the  heads    occur   singly  at  the   ends  of  long,   few-bracted 
peduncles  that  terminate  the  main  stem  and  branches. 

(2)  The  Involucre. — In  the  Compositse  the  heads  are  subtended 
by  an  involucre  consisting  of  bracts,  usually  numerous  and  ar- 
ranged in  one  or  more  circles.     In  this  case  the  involucre  is  flat- 
tish  or  slightly  convex  below  and  composed  of  scales  imbricated 
in  several  rows.     The  component  scales  are  linear-lanceolate  and 

169 


170  LABORATORY    EXERCISES    IN    BOTANY. 

scarious  on  their  margins  and  at  their  tips.  They  doubtless  rep- 
resent the  bracts  of  what  were  in  the  remote  ancestors  of  these 
plants  a  much  looser  inflorescence,  but  which  in  course  of  time 
became  concentrated  into  a  head. 

(3)  The  flowers  or  florets  are  individually  quite  small,  and,  as 
in  many  other  of  the  Composite,  are  of  two  kinds — marginal 
ones  which  are  relatively  large  and  showy  and  are  called  ray- 
flowers,  and  interior,  smaller,  and  less  showy  ones  which  are 
called  disk-flowers.  The  ray-flowers  have  lignlate  and  the  disk- 
flowers  tubular  corollas.  In  some  Composite,  as  the  Dandelion 
and  Chicory,  the  florets  are  all  of  one  kind  and  ligulate,  while 
in  others,  as  in  the  Burdock  and  Boneset,  they  are  all  tubular. 

(a)  The  common  receptacle  on  which  the  florets  are  arranged  is 
flat  or  slightly  convex  and  naked  ;  that  is  to  say,  no  chaff  or  scales 
occur  upon  it  among  the  flowers  as  they  do  in  many  other  species 
of  the  order.  It  will  be  observed  that  the  florets  are  regularly 
arranged  on  the  receptacle  in  spirals. 

(6)  The  ray-flowers  are  white,  the  corolla  two-nerved,  obscurely 
two-  or  three-toothed  at  the  apex,  contracted  and  tubular  below, 
near  its  insertion  on  the  top  of  the  ovary,  and  is  from  ten  to 
eighteen  millimetres  in  length.  These  flowers  are  usually  in  one 
or  two  circles,  and  there  are  from  twenty  to  thirty  of  them  in 
each  head. 

In  all  the  Compositse  the  corollas  and  stamens  are  epigynous 
and  the  tubular  calyx  (or  receptacle)  is  adnate  to  the  ovary.  The 
calyx-limb,  if  present,  is  ring-like,  chaffy,  bristly  or  scaly,  and  is 
termed  a  pappus.  In  the  present  instance  it  is  usually  wanting 
altogether,  though  sometimes  recognizable  as  a  minute  scale. 

The  two-lobed  stigma  and  the  upper  part  of  the  cylindrical  style 
project  from  the  tubular  portion  of  the  corolla  as  shown  on  Plate 
XXV.  (Fig.  2),  but  the  stamens  are  altogether  wanting  in  the 
ray-flowers. 

The  ovary  is  obovoid  in  outline  and  longitudinally  striate. 

(c)  The  disk-flowers  are  very  numerous — often  four  or  five  hun- 
dred in  a  single  head  ;  they  are  yellow,  with  a  five-toothed  limb 
the  teeth  of  which  are  valvate  in  the  bud,  and  have  a  tube  which 
is  somewhat  inflated  and  bell-shaped  above,  contracted  a  little 
below  the  middle,  and  airain  slightly  inflated  a  little  above  the 
ovary.  The  bottom  part  of  the  tube  is  filled  with  nectar.  The 


STUDY   OF   A    FLOWER   OF   THE    COMPOSITE.  171 

corolla  is  much  smaller  than  that  of  the  ray-flowers — only  about 
three  millimetres  in  length.  The  florets  possess  both  stamens  and 
pistils,  the  former  five  in  number  and  united  by  their  enlougated 
anthers  into  a  tube  which  surrounds  the  style.  The  filaments  are 
thread-like,  free,  and  inserted  on  the  corolla-tube.  The  anthers 
are  two-celled,  introrse,  innate,  and  longitudinally  dehiscent. 

The  pistil  is  similar  to  that  of  the  ray-flowers.  A  cross-section 
of  the  ovary  shows  but  a  single  ovule,  and  a  longitudinal  section 
shows  that  this  is  erect  and  auatropous. 

The  Compositse  are  the  most  numerous  in  species  of  all  flower- 
ing plants,  and  are  among  the  most  highly  organized.  They  are 
almost  without  exception  entomophilous,  sometimes  dioecious, 
more  commonly  perfect  and  protandrous.  The  aggregation  of  a 
large  number  of  small  flowers  in  a  head  is  a  great  advantage,  for 
it  accomplishes  the  purpose  of  being  attractive  to  the  eyes  of  in- 
sects with  little  expenditure  of  material  for  the  individual  florets. 
It  is  also  economical  in  another  way :  the  compact  arrangement 
of  the  flowers,  enabling  the  insect  to  sip  from  a  large  number  in 
a  short  space  of  time  and  at  a  single  visit,  enhances  the  chances 
of  cross-fertilization. 

In  most  of  the  order  a  brush  of  hairs  exists  either  on  the  upper 
part  of  the  style  or,  as  in  this  species,  on  the  outer  sides  of  the 
stigma-lobes.  Since  the  style  does  not  complete  its  growth  in 
length  until  after  the  anthers  dehisce,  its  elongation  brushes  out 
from  the  narrow  staminal  tube  the  pollen,  which  emerges  along 
with  the  still  closed  stigma  at  the  top  of  the  floret  and  is  gathered 
up  by  insects.  Later  on,  the  lobes  of  the  stigma  open  out  and 
expose  their  stigmatic  surfaces  to  the  pollen  brought  by  visiting 
insects.  In  this  species,  and  probably  in  many  other  Compositse 
with  perfect  flowers,  self-fertilization  is  possible,  and  probably 
sometimes  occurs,  but  cross-fertilization,  frequently  between  florets 
of  the  same  head,  but  often  from  flowers  of  different  heads  and 
from  other  plants  of  the  species,  must  be  habitual.  According  to 
Prof.  Hermann  Miiller,  as  many  as  seventy-two  different  species 
of  insects  have  been  observed  to  visit  the  flowers  of  this  plant. 


STUDY   OF    A    FLOWER   OF    THE   COMPOSITE.  173 


al? 


b  — 


PLATE  XXV.,  FIG.  1.— Flower-head  of  Ox-eye  Daisy  (about  natural  size),  cut  longi- 
tudinally to  show  arrangement  of  parts:  a,  one  of  the  ray-florets ;  b,  a  disk-floret;  c,  the 
common  receptacle ;  d,  the  hollow  peduncle. 

FIG.  2.— One  of  the  Ray -florets  (considerably  enlarged) :  a,  two-lobed  stigma ;  b,  ovary 
surmounted  by  the  corolla-tube. 

FIG.  3.— One  of 'the  Tubular  Disk-florets  (much  enlarged). 

FIG.  4.— Pistil  with  fully-developed  Style  and  Stigma.    (Much  enlarged.) 

FIG.  5.— Sta-minal  Tube  laid  open  and  exposing  inner  face  of  Anthers. 


EXERCISE  XXII. 

STUDY  OF  A  MONOCHLAMYDEOUS  FLOWER 

THE  following  plants  are  favorable  ones  for  study  :  Wild  Gin- 
ger (Asarum  Cauadense,  L.\  Pipe  Vine  (Aristolochia  Sipho, 
L'H&r.),  Buckwheat  (Fagopyrum  esculentum,  Moench),  Four- 
o'clock  (Mirabilis  Jalapa,  L.),  and  Pokeweed  (Phytolacca  decan- 
dra,  L.). 

From  the  above-mentioned  is  selected  for  this  study  the  Wild 
Ginger,  a  member  of  the  Birthwort  family,  and  a  plant  which  is 
not  uncommon  in  rich  woods  in  the  northern  part  of  the  United 
States,  and  which  blossoms  in  May.  It  produces  rhizomes  which 
creep  extensively  near  the  surface  of  the  ground  and  which  branch 
frequently  as  in  Podophyllum,  giving  rise  to  new  plants.  These 
rhizomes  are  nearly  cylindrical  or  somewhat  quadrangular,  marked 
at  intervals  of  about  twelve  millimetres  with  prominent,  more  or 
less  oblique  scale-scars,  and  on  their  under  surface,  mostly  from 
the  nodes,  producing  small  clusters  of  slender,  nearly  simple 
rootlets  averaging  about  sixty  millimetres  in  length.  A  cross- 
section  of  a  rhizome  shows  a  thin  circle  of  wood  enclosing  a  large 
pith  and  composed  of  about  twelve  short  wood-bundles.  The 
iodine  test  shows  it  to  contain  abundance  of  starch.  Besides 
some  bitterness,  it  is  pungently  aromatic,  reminding  one  of  gin- 
ger, hence  the  popular  name  of  the  plant. 

The  end  of  the  rhizome  rises  obliquely  to  form  the  very  short 
above-ground  stem,  and  this  bears  two  long-petiolate,  exstipulate 
leaves  whose  blades  are  broadly  reni/brm,  entire-margined,  and 
slightly  pointed  at  the  apex.  The  blades  are  thin,  have  a  trans- 
verse diameter  of  from  ten  to  twelve  centimetres,  are  deep-green 
and  silky  lustrous  by  reason  of  a  minute  pubescence  on  the  upper 
surface,  and  are  lighter  colored  and  prominently  veiny  below. 

From  between  the  two  leaf-bases  issues  a  single  pedunculate, 
nodding,  dull-purple  flower,  which,  together  with  the  peduncle,  is 
densely  covered  on  the  outside  with  a  woolly  pubescence. 

175 


17<i  LABORATORY   EXERCISES   IN   BOTANY. 

(1)  The  calyx  is  rather  fleshy,  with  a  tube  adnate  to  the  ovary, 
and  a  three-parted  limb  the  segments  of  which,  in  the  bud,  have 
their  tips  inflexed,  but  which  are  wholly  recurved  when  the  flower 
is  in  full  blossom. 

Search  is  made  in  vain  for  a  corolla.  This  organ  is  in  fact 
entirely  wanting.  When  one  set  of  the  floral  envelopes  is  lack- 
ing, it  is  usually,  as  in  this  case,  the  corolla.  Such  flowers,  since 
'they  possess  but  one  whorl  of  floral  envelopes,  are  called  mono- 
vhlamydeous. 

(2)  The  Androedum. — Counting  the  stamens,  they  are  found  to 
be  twelve  in  number,  but  careful  observation  shows  that  six  of 
them  are  shorter  than  the  other  six,  and  that  they  are  inserted  at 
a  slightly  lower  level  than,  and  alternate  with,  the  remaining  six. 
They  are  therefore  to  be  regarded  as  occurring  in  two  whorls  of 
six  stamens  each.     Each  of  the  stamens  has  a  color  similar  to 
that  of  the  calyx,  and  each  is  provided  with  a  short,  thickisb, 
outwardly-curved  filament  and  a  two-celled,  adnate,  and  extrorse 
anther  whose  connective  is  conspicuously  prolonged  and  pointed. 
The  anthers  dehisce  longitudinally. 

(3)  The  Gyncecium. — The  pistil  is  provided  with  a  short,  thick, 
fleshy  style  that  is  crowned  with  a  six-lobed  stigma.     Making  a 
cross-section  of  the  ovary,  it  is  found  to  be  distinctly  six-celled, 
with  several  ovules  in  each  cell.    These  ovules,  it  will  be  observed, 
are  attached  to  the  axis  or  central  column  of  the  ovary,  so  the 
placentatiou  is  denominated  axile  or  axillary.     Such  a  pistil  is 
clearly  six-carpeled,  and  in  numerical  plan  corresponds,  therefore, 
with  the  andrcecium.     It  may  well  be  supposed  to  be  made  up  as 
follows:  the  iuturned  edges  of  the  carpellary  leaves  have  grown 
toward  the  centre  and  met  there,  thus  forming  the  partitions  and 
central  column  and  accounting  for  the  axile  placentation  of  the 
ovules,  which  are  really  borne  on  the  infolded  edges  of  the  leaves, 
as  has  been  observed  in  the  Goldthread  and  Sweet  Pea.     If,  in 
fact,  study  be  made  of  the  very  young  ovary  of  Asaruni,  it  will 
be  found  to  have  six  marginal  placenta?,  each  with  a  double  row 
of  ovules  on  its  edge.     It  is  only  later  that  these  placentae  become 
prolonged  so  as  to  meet  in  the  centre  and  form  the  axile  placenta- 
tion observed  in  the  mature  pistil.     The  law  governing  the  struc- 
ture of  the  compound   pistil  is  thus  the  same  as  that  governing 
the  structure  of  the  simple  one. 


STUDY   OF    A    MONOCHLAMYDEOUS    FLOWER.  177 

(4)  Numerical  Plan  and  Affinities. — The  peculiarities  of  struc- 
ture thus  far  ascertained  raise  some  questions  as  to  the  numerical 
plan  and  the  affinities  of  the  plant.  Is  the  number  plan  three  or 
six?  The  sepals,  as  has  been  observed,  were  three  in  number — 
or,  rather,  the  calyx,  being  parted  into  three  segments,  indicates 
a  construction  on  the  numerical  plan  of  three ;  but  both  stamens 
and  pistils  indicate  a  numerical  plan  of  six.  One  might  suppose 
the  stamens  to  have  been  originally  in  four  whorls  of  three  each, 
which  were  afterward  condensed  into  two  of  six  each,  and  that  a 
similar  condensation  took  place  in  the  case  of  the  pistils.  The 
numerical  plan  would  then  be  that  of  three.  But  there  is  the 
alternative  supposition  that  the  calyx  is  the  organ  that  has  varied 
from  the  original  plan,  and  that  the  numerical  plan  is  to  be  re- 
garded as  that  of  six. 

If  the  former  supposition  be  accepted,  is  the  plant  a  monocotyl 
or  a  dicotyl?  Monocotyls,  as  has  been  noted,  almost  always  have 
their  flowers  arranged  on  the  numerical  plan  of  three,  while  in 
dicotyls  this  plan  is  very  rare.  Observing  the  leaves,  the  vena- 
tion is  found  to  be  netted  ;  studying  the  stem,  its  vasal  bundles 
are  found  arranged  in  a  circle;  there  is  a  cambium  zone,  there  are 
medullary  rays  and  a  pith, — facts  all  of  which  point  to  the  affini- 
ties of  the  plant  with  dicotyls.  .  If,  further,  the  seed  be  dissected, 
there  is  found — though  with  difficulty,  because  it  is  minute — a 
dicotyledonous  embryo,  which  is  most  conclusive  proof  that  the 
plant  is  a  dicotyl. 

But  the  question  remains,  Is  three  or  six  the  numerical  plan  of 
the  flower  ?  It  seems,  on  the  whole,  more  reasonable  to  conclude 
that  six  is  the  number,  because  this  number  is  not  rare  among 
dicotyls,  and  because,  moreover,  it  is  more  reasonable  to  suppose 
that  one  set  of  organs  (the  calyx)  has  deviated  from  the  plan  than 
that  two  sets  (stamens  and  pistil)  have  done  so. 

Let  the  student  now  make  a  careful  study  and  drawings  of  one 
of  the  other  plants  mentioned  in  the  list  at  the  beginning  of  this 
exercise. 
12 


STUDY    OF    A    MONOCHLAMYDEOUS    FLOWER. 


179 


PLATE  XXVI.,  FIG.  1.— Plant  of  Asarum  canadense  (%  natural  size),  showing  rhizome 
with  its  scale-scars  and  rootlets,  the  two  large  leaves,  and  the  single,  terminal,  nodding 
flower. 

FIG.  2.— Diagram  of  the  Cross-section  of  the  Stem,  showing  the  interrupted  circle  of 
vasal  bundles,  the  pith,  and  the  thickish  cortex. 

FIG.  3.— Longitudinal  section  through  the  centre  of  the  flower,  the  adherent  calyx- 
tube,  the  epigynous  arrangement  of  the  stamens,  etc. :  a  is  one  of  the  segments  of  the 
calyx ;  b,  the  stigma ;  and  c,  the  ovary  with  its  ovules. 

FIG.  4.— Ground  Plan  of  Flower. 

FIG.  5. — One  of  the  Stamens,  showing  adnate  anther  and  prolonged  connective. 


EXERCISE  XXIII. 

STUDY  OF  A  LILIACEOUS  FLOWER:   THE  MONOCOTYL  TYPE. 

SELECTIONS  may  be  made  from  the  following  common  plants : 
the  Tiger  Lily  (Lilium  tigrinum,  Ker),  the  Wild  Orange  Red  Lily 
(Lilium  Philadelphia m,  L.),  the  TurkVcap  Lily  (Lilium  super- 
bum,  L.\  the  Indian  Cucumber  (Medeola  Virginica,  L.),  the 
Large-flowered  Trillium  (Trillium  grandiflorum,  Salisb.),  the 
Erect  Trillium  (Trillium  erectum,  L.),  the  American  White 
Hellebore  (Veratrum  viride,  Ait.),  the  Wild  Onion  (Allium  cer- 
nuum,  Roth),  the  Star  of  Bethlehem  (Oruithogalum  umbellatum, 
L.),  the  Wild  Hyacinth  (Camassia  Frazeri,  Torr.),  the  Bell  wort 
(Uvularia  perfoliata,  L.),  and  the  Yellow  Adder's-tongue  (Ery- 
thronium  Americanum,  Ker). 

The  last-named  plant  on  this  list  shall  serve  the  present  pur- 
pose. The  Yellow  Adder's-tongue  is  a  common  plant  in  the 
northern  and  eastern  portions  of  the  United  States  and  Canada, 
where  it  grows  in  rich  woods,  blossoming  in  early  spring. 

The  underground  parts  consist  of  a  deeply-buried  tunicated 
bulb  and  numerous  nearly  simple,  fibrous,  adventitious  roots 
which  are  emitted  from  its  lower  end.  In  the  sterile  plant  this 
bulb  usually  sends  up  but  a  single  leaf,  but  in  the  flowering  one 
two  apparently  opposite,  but  really  alternate,  ones.  These  are 
each  about  four  inches  long,  lanceolate,  oblanceolate,  or  elliptic- 
lanceolate,  entire,  acute,  thickish,  with  an  indistinct  basi-nerved 
venation,  smooth  and  light-green,  with  darker  green  or  purplish 
irregular  spots  on  both  surfaces.  The  leaves  taper  below  into 
long  petioles,  the  outer  or  lower  of  which  ensheathes  the  next, 
and  this  in  turn  the  long,  naked,  cylindrical  scape.  The  latter 
rises  to  the  height  of  five  or  six  inches,  and  bears  at  its  apex  a 
single  yellow,  nodding  flower. 

(1)  The  anthotaxy  is  therefore  solitary  and  determinate. 

(2)  The  prefloration,  if  the  perianth  be  studied  carefully,  is  found 
to  be  valvate  in  the  first  whorl  and  imbricate  in  the  second. 

181 


182  LABORATORY    EXERCISES    IN    BOTANY. 

(3)  The  perianth  is  in  fact  composed  of  two  whorls  of  three 
pieces  each,  the  outer  set  representing  the  calyx  and  the  inner 
one  the  corolla,  for  close  inspection  shows  that  the  former  differs 
from  the  latter  slightly  in  size,  shape,  and  depth  of  coloring,  as 
well  as  in  prefloration.     The  pieces  are  all  distinct  or  not  at  all 
united  with  each  other;  the  calyx  and  the  corolla  therefore  arc 
chorisepalous  and  choripetalous  respectively.     They  are  both  in- 
serted upon  the  receptacle  beneath   the  pistil,  and  are  therefore 
hypogynous.     Each   piece  is  lanceolate  in  form,  and,  when  the 
flower  is  in  full  blossom,  outwardly  curved,  or  reflexed. 

(4)  The  andrcecium  consists  of  six  distinct  pieces  also  arranged 
in  two  whorls,  the  outer  of  these  opposite  the  sepals  and  the  inner 
opposite  the  petals.     They  are  also  hypogynous.     Each  stamen 
consists  of  a  filament  which  is  flattened  below  and  narrowed  to  a 
slender  point  above,  and  an  oblong,  two-lobed  and  two-celled,  in- 
trorse  anther.     The  anther,  being  inserted  by  its  base  on  the  end 
of  the  filament,  is  said  to  be  innate.     It  opens  to  shed  the  pollen 
by  means  of  a  slit  running  lengthwise  of  each  cell,  and  the  dehis- 
cence  is  therefore  said  to  be  longitudinal.     The  pollen,  it  will  be 
observed,  is  adhesive,  and  this,  together  with  the  showiness  of  the 
perianth,  leads  one  to  conclude  that  the  flower  is  adapted  to  cross- 
fertilization  by  insect  agency.     That  it  must  be,  occasionally  at 
least,  fertilized  by  its  own  pollen  is,  however,  sufficiently  indicated 
by  the  fact  that  the  stamens  face  inward  and  open  in  such  close 
proximity  to  the  stigmas,  and  by  the  fact  that  the  latter  are  recep- 
tive simultaneously  With  the  shedding  of  the  pollen. 

(5)  The  gyncedum  consists  of  a  single  pistil  which  is  complete 
in  its  parts,  possessing  an  ovary,  a  style,  and  a  stigma.    The  o van- 
is  ellipsoidal  or  obovate  in  form,  contracted  into  a  short  stalk  at 
the  base,  and  longitudinally  three-lobed.    The  style  is  club-shaped, 
slender  and  somewhat  bent  below,  and  thick  and  obscurely  three- 
lobed  longitudinally  in  its  upper  portion.     In  height  it  attains 
about  the  same  level  as  the  top  of  the  anthers.     The  stigma  is 
terminal,  and  consists  of  a  three-lobed  papillose  area  at  the  apex 
of  the  style. 

The  ovules  are  numerous,  horizontal,  and  anatropous,  though 
the  latter  fact  is  not  easily  determined  with  an  ordinary  magnify  - 
ing-glass. 

Here  is  a  single  pistil  where  one  would  naturally  expect  three. 


STUDY    OF   A   LILIACEOUS    FLOWER.  183 

But  even  a  superficial  inspection  shows  that  the  single  organ  is 
probably  formed  by  the  coalescence  of  three,  for  the  stigma,  as  has 
been  seen,  the  upper  part  of  the  style,  and  the  ovary  are  each 
three-lobed.  Moreover,  the  lobes  alternate  with  the  inner  set 
of  stamens,  as  would  be  the  case  if  the  compound  pistil  were 
formed  by  the  coalescence  of  three  simple  ones.  But  confirma- 
tory evidence  of  the  correctness  of  the  view  that  the  pistil  is  three- 
carpeled  is  obtained  by  studying  the  cross-section  of  the  ovary. 
This  section  shows  three  loculi,  each  containing  a  double  row 
of  ovules  arranged  vertically  along  the  inner  side  of  the  loculus 
— an  axillary  placentation,  in  fact,  as  in  Asarum.  This  is  the 
precise  arrangement  which  would  result  if  three  carpellary  leaves 
were  folded  inward  until  the  edges  touched  at  the  centre  and  a 
row  of  ovules  were  borne  on  each  infolded  edge. 

The  flower,  therefore,  is  really  constructed  throughout  on  the 
numerical  plan  of  three ;  and,  since  there  are  five  whorls  of  three 
each,  all  alternating  with  each  other,  it  is  wholly  symmetrical.  It 
is,  in  fact,  a  nearly  typical  or  pattern  flower,  the  only  real  deviation 
being  a  slight  irregularity  shown  in  the  shape  of  the  pistil.  This 
is  related  to  the  nodding  position  of  the  flower,  and  both  are  doubt- 
less adaptations  to  cross-fertilization  by  insect  agency.  In  this 
flower  the  deviation  is  but  slight.  In  many  other  monocotyls,  as 
in  some  orchids,  it  has  become  extreme,  so  that  there  is  not  only 
great  irregularity  in  the  shape  and  coloring  of  parts,  but  great  dis- 
symmetry also,  often  obscuring  even  the  numerical  plan. 

(6)  The  Monocotyl  Type  of  Flower. — Except  for  its  slight  irreg- 
ularity, the  flower  of  the  Adder's-tongue  may  be  regarded  as  a 
flower  typical  of  monocotyl  plants,  as  the  Flax  and  Sedum  are 
of  dicotyls.  In  all  this  vast  group  the  flowers  appear  to  have 
been  constructed  on  the  numerical  plan  of  three  and  on  the  basis 
of  five  alternating  whorls — one  of  sepals,  one  of  petals,  two  of 
stamens,  and  one  of  pistils.  In  course  of  time  many  species  have 
developed  irregularities  and  dissymmetries,  as  has  been  seen  among 
dicotyls,  but  seldom  is  the  original  plan  completely  obscured  ;  and, 
since  the  flowers  of  dicotyls  are  rarely  constructed  on  the  numerical 
plan  of  three,  the  one  group  of  plants  may  almost  always  easily 
be  distinguished  from  the  other  by  observing  the  numerical  plan 
of  the  flowers. 


STUDY   OF    A    LILIACEOUS   FLOWER. 


185 


PLATE  XXVII.,  FIGS.  1,  2.— Flowering  Plant  of  Erythronium  Americanum  (%  natural 

size). 

FIGS.  3,  4.— Ground  Plan  and  Vertical  Section  respectively  of  the  Flower. 
FIG.  5. — One  of  the  Stamens  shown  in  dorsal  (a)  and  in  ventral  (6)  view. 

FIG.  6.— Pistil :  a,  stigma  ;  6,  enlarged  upper  portion  of  style ;  c,  contracted  and  some- 
what bent  lower  part  of  style  ;  d,  ovary  ;  e,  torus. 


EXERCISE  XXIV. 

FLOWERS  OF  MONOCOTYLS  (CONTINUED). 

IN  connection  with  the  study  of  a  liliaceous  flower,  which  has 
been  taken  as  typical  of  the  monocotyls,  one  may  profitably 
;study  some  of  the  flowers  from  related  families  in  which  the  type 
has  undergone  modifications  more  or  less  important.  Selections 
may  be  made  from  the  AmaryllidaceaB  and  from  the  Orchidacese, 
as  follows  :  Amaryllidacece :  the  Daffodil  (Narcissus  Pseudo-nar- 
cissus, L.),  the  Poet's  Narcissus  (Narcissus  poeticus,  Salisb.),  the 
Jonquil  (Narcissus  Jonquilla,  Willd.),  the  Polyanthus  (Narcissus 
Tazetta,  Willd.),  or  the  Pancratium  (Pancratium  maritimum,  L.}. 
OfcJtidacece :  the  showy  Orchis  (Orchis  spectabilis,  L.),  the  Yel- 
low Fringed  Orchis  (Habenaria  ciliaris,  R.  Br.),  the  Fragrant 
Orchis  (Habenaria  leucophsea,  Gray),  the  Arethusa  (Arethusa 
bulbosa,  L.),  the  Calopogon  (Calopogon  pulehellus,  R.  Br.),  the 
Pogonia  (Pogonia  ophioglossoides,  Nutt.),  the  Showy  Lady's  Slip- 
per (Cypripedium  spectabile,  Salisb.),  the  Yellow  Lady's  Slipper 
(C.  pubescens,  Willd.),  or  the  Stemless  Lady's  Slipper  (C.  acaule, 
Ait.). 

PART  I. — From  these,  for  the  first  study,  a  selection  is  made 
-of  the  commonly  cultivated  Narcissus  poeticus.  This  is  a  spring- 
blooming  plant  with  long,  linear,  parallel- veined,  radical  leaves 
which  arise  from  a  tunicated  bulb.  The  flowers  occur  in  a  few- 
flowered  umbel  at  the  end  of  a  scape,  and  the  cluster  is  subtended 
at  its  base  by  a  conspicuous,  scale-like  bract  or  spathe. 

(I)  The  perianth,  as  in  the  Erythronium,  is  composed  of  six 
pieces,  and  these  also  are  in  two  whorls  of  three  each  which  alter- 
nate with  each  other,  but  the  pieces  have  grown  together  at  their 
base  to  form  a  long  tube,  so  that  the  perianth  is  hypocrateriform. 
This  growing  together  of  parts,  either  of  the  same  or  of  different 
whorls,  constitutes  one  of  the  common  ways  in  which  many  flow- 
-ers  have  come  to  differ  from  the  type.  But  the  adhesion  is  car- 

187 


1SS  LABORATORY   EXERCISES   IN   BOTANY. 

ried  still  farther  in  this  instance.  It  will  be  observed  that  the 
perianth  seems  to  spring  from  the  top  of  the  ovary  instead  of 
arising  from  the  receptacle  at  its  base.  Unquestionably,  in  the 
remote  ancestors  of  the  plant  it  was  hypogynous,  as  in  Ery thro- 
mum,  but  in  course  of  time  it  has  become  adnate  to  the  ovary, 
so  as  to  seem  to  arise  from  its  top,  and  is  not  therefore  inappro- 
priately described  as  epigynous. 

(2)  The  corona  constitutes  another  difference  between  this 
flower  and  that  of  Erythronium.  This  is  a  tubular  or  cup- 
shaped  appendage  arising  from  the  throat  of  the  perianth,  and 
shown  in  section  on  Plate  XXVIII.  (Fig.  3,  a).  The  real  nature 
of  this  organ  is  not  easily  determined,  and  various  theories, 
more  or  less  plausible,  have  been  advanced  to  account  for  it. 
By  some  the  corona  is  regarded  as  consisting  of  two  or  more 
whorls  of  petals  which  have  coalesced.  As  it  is  a  not  uncom- 
mon thing  for  the  whorls  of  the  corolla  to  be  multiplied  beyond 
the  normal  number,  there  is  some  reason  in  favor  of  the  view, 
though,  if  this  be  its  origin,  it  is  difficult  to  understand  why  there 
should  be  such  an  abrupt  transition  from  one  kind  of  petaline  whorl 
to  another.  If  this  were  the  case,  one  would  expect  to  find  in  some 
members  of  the  large  Amaryllis  family  flowers  in  which  there  were 
forms  transitional  between  the  proper  petals  and  the  corona,  but 
this  is  not  the  case.  Others  regard  the  corona  as  made  up  of  stam- 
inodes,  or  abortive  stamens,  belonging  to  two  or  more  whorls  out- 
side the  regular  ones.  But  there  are  the  same  objections  to  this  as 
to  the  view  just  mentioned,  the  two  whorls  normally  present  in 
mouocotyls  being  present  here  and  being  nearly  normal  in  their  de- 
delopment.  Others  still  regard  the  corona  as  identical  in  its  nature 
with  the  crown  which  is  present  in  many  flowers  of  the  Pink 
family,  where  it  undoubtedly  represents  the  stipules  of  the  corol- 
line  leaves.  The  fact  that  in  some  species  of  Narcissus  the  crown 
is  more  or  less  distinctly  twelve-pointed,  making  two  stipules  for 
each  leaf  of  the  perianth,  gives  to  this  view  much  probability. 
Moreover,  if  the  ligule  of  grasses  be  regarded  as  consisting  of  a 
pair  of  modified  stipules,  one  may  easily  trace  a  close  parallelism 
between  it  and  the  corona  of  this  plant, 

But  still  another  view  is  that  the  corona  is  in  the  nature  of  a 
disk  such  as  is  present  in  the  flower  of  the  Orange,  and  which  also 
occurs  in  many  other  plants,  both  dicotyls  and  monocotyls.  This 


FLOWERS    OF    MONOCOTYLS.  189 

disk  is  sometimes  hypogynous  as  in  the  Orange,  sometimes  perigy- 
nous  as  iu  Buckthorn,  and  sometimes  epigynous  as  in  the  Umbel- 
liferse.  In  the  latter  case  it  may  rise  considerably  above  the  level 
of  the  ovary,  and  form  a  crown-like  ridge  or  elevation  as  in  Pe- 
liosanthes.  The  reasons  for  believing  that  the  crown  of  Narcissus 
may  be  of  this  character,  despite  its  membranous  texture  and  petal- 
oid  appearance,  are  derived  from  a  study  of  its  development.  It 
begins  later  than  do  the  other  floral  organs,  as  a  slight  ring-like 
elevation  between  the  stamina!  whorls  and  those  of  the  androe- 
cium,  and  wholly  independent  of  both.  By  its  growth  perianth 
and  audroecium  are  carried  up  together,  forming  the  common  tube 
which  both  envelops  the  ovary  and  is  carried  much  beyond  it,  the 
crown,  according  to  this  view,  being  only  the  free  portion  of  this 
remarkably  developed  disk.  This  is  the  view  of  M.  Baillon,  and 
as  such  must  command  great  respect.  But  it  seems  to  the  author 
that  the  facts  Baillon  states  regarding  the  development  of  the  disk 
are  not  inconsistent  with  the  view  that  the  corona  represents  the 
coalesced  stipules  of  the  perianth  leaves.  The  stipules,  as  well  as 
the  other  parts,  may  have  been  carried  up  by  the  development  of 
the  disk.  Their  texture  and  the  fact  that  they  are  sometimes 
twelve-toothed  seem  more  in  accord  with  this  view. 

But,  after  all,  it  is  of  less  importance  what  view  be  adopted 
than  that  the  process  of  reasoning  by  which  the  view  is  arrived 
at  be  understood. 

(3)  The  andrcecium  here,  as  in  Erythronium,  consists  of  two 
whorls  of  three  stamens  each,  but,  instead  of  being  borne  on  the 
receptacle  beneath  the  ovary,  they  have  become  adnate  by  their 
filaments  to  the  perianth-tube,  one  set  of  anthers  appearing  near 
its  throat  and  the  other  near  the  middle  of  the  tube.     The  free 
portions  of  the  filaments  are  very  short,  but  they  may  be  traced 
along  the  line  of  their  attachment  to  the  tube  clear  to  the  base  of 
the  latter.     The  anthers  are  two-lobed,  two-celled,  iutrorse,  and 
attached  to  the  filaments  near  their  middle. 

(4)  The  gyncecium  in  most  respects  resembles  that  of  Erythro- 
nium except  for  the  adnate  perianth-tube  and  the  slender,  straight 
style,  the  ovary  being  three-lobed,  three-celled,  mauy-ovuled,  and 
with  an  axile  placentation. 

The  flower,  like  that  of  Erythronium,  is  also  nearly  regular, 
but  shows,  by  being  bent  on  its  peduncle  and  by  being  somewhat 


190  LABORATORY    EXERCISES    IX    BOTANY. 

bent  just  above  the  ovary,  so  as  to  face  laterally,  a  slight  tendency 
toward  irregularity. 

In  the  Narcissus,  then,  may  be  seen  a  flower  that  in  numerical 
plan  and  in  the  relative  arrangement  of  its  parts  conforms  to  the 
monocotyl  type,  and  deviates  from  the  latter  only  in  the  develop- 
ment of  a  corona,  in  the  growing  together  of  its  parts,  and  in  the 
development  of  a  slight  irregularity. 

PART  II. — Now  let  there  be  compared  with  the  structure  of 
the  flowers  of  Erythrouium  and  Narcissus  that  of  one  of  the 
Orchidaceae,  selecting  for  the  purpose  Cypripedium  acaule.  This 
plant,  which  is  one  of  the  commoner  species  of  this  curious  genus, 
grows  in  low,  sandy  regions  throughout  the  eastern  and  northern 
portions  of  the  United  States.  From  its  small,  contorted  rhizome 
issue  numerous  tufted,  simple,  crinkled  rootlets,  twelve  or  fifteen 
centimetres  long,  and  from  its  apex  a  flowering  stem  or  scape  which 
rises  to  the  height  of  fifteen  or  twenty  centimetres  and  bears  leaves 
only  at  its  base.  These  consist,  first,  of  two  or  three  scales,  and 
then  of  two  sheathing,  simple,  glandular-hairy  foliage-leaves. 
The  conspicuous  purple  flowers  occur  singly  at  the  end  of  the 
scape,  and  each  is  subtended  by  a  bract.  The  flowers  are  nod- 
ding, and  the  different  floral  organs  are  borne  on  the  top  of  the 
ovary  or  are  epigynous,  as  in  Narcissus ;  but  here  the  resem- 
blance apparently  ends,  for  the  flower  has  become  strangely 
unsymmetrical  and  irregular. 

(1)  The  8epals  are  apparently  but  two  in  number,  whereas  one 
would  expect  three.       If  the  lower  sepal,  however,  be  observed 
closely,  there  will   be  found   indications   in  its  venation  of  the 
coalescence  of  two,  and  sometimes  further  evidence  of  the  same 
thing  in  the  form  of  a  slight  notch  at  its  apex.     In  some  other 
species,  as  in  Cypripedium   pubescens,  this  notch  is  much   more 
conspicuous,  and  in  Cypripedium  arietiuum  the  three  sepals  are 
entirely  distinct,  as  they  are  in  Erythronium.     The  sepals,  then, 
are  really  all  present  here,  but  the  fact  is  obscured  by  the  more 
or  less  complete  coalescence  of  two  of  them. 

(2)  The  corolla  is  much   more  profoundly  changed.     The  two 
lateral  petals  are  normally  developed,  though  greenish  in   color, 
and   are    linear-lanceolate,  somewhat   twisted    bodies,   while   the 
lower  one,  in  the  ordinary  position  of  the  flower,  is  an  enormously 


FLOWERS    OF    MONOCOTYLS.  191 

developed  sac  or  moccasin-like  body  of  a  purple  color,  and  totally 
different  in  appearance  from  the  other  two.  This  is  called  the 
labellum. 

(3)  The  column,  as  it  is  called,  is  at  its  base  a  stout  cylinder 
rising  from  the  centre  of  the  corolline  whorl,  and  bearing  on  its 
upper  side  a  thick,  spade-shaped  or  somewhat  rhomboidal  body 
near  the  base  of  which,  on  either  side,  lie  two  gland-like  bodies 
which,   however,  are   really  stamens.      The   spade-shaped  body 
arches  over  a  faintly  and    unequally  three-lobed   stigma  which 
faces   downward   and  terminates  the  column.       In   this    organ, 
then,  stamens  and  pistils  have  grown  together  or  become  adnate, 
and  the  arrangement  is  described  as  a  gynandrous  one. 

(4)  The  andrcecium  apparently  consists  of  but  the  two  gland-like 
stamens;  but  what  has  become  of  the  other  four?     And  do  the 
two  which  are  present  belong  to  the  inner  or  to  the  outer  whorl  ? 
What  is  the  nature  of  the  spade-shaped  body  ?     Does  it  repre- 
sent a  petal  or  a  stamen,  or  is  it  an  outgrowth  from  the  receptacle 
in  the  nature  of  a  disk  ?     These  questions  can  be  answered  only 
by  carefully  studying  the  development  of  the  flower,  by  compar- 
ing it  with  those  of  related  plants,  and  by  the  study  of  those 
monstrosities  which  sometimes  occur  and  indicate  a  return  to  an 
ancestral  and  more  regular  condition.    It  frequently  happens  both 
among  animals  and  plants  that  an  organ  that  has  become  rudi- 
mentary and  tends  to  disappear  suddenly  appears   fully  devel- 
oped ;   or  that  one  which  has  become  strongly  irregular   devel- 
ops regularly  ;  or  that  one  which  has  disappeared  entirely  reap- 
pears.   Thus,  in  some  Scrophulariacese  there  is  a  rudimentary  and 
functional  fifth  stamen  which  in  rare  instances  develops  into  the 
ordinary  form,  or  the  petal  of  a  Trillium  or  a  Rose  develops  into 
an  ordinary  green  leaf;  and  instances  are  on  record  where  a  Cypri- 
pedium  has  developed  a  perianth  perfectly  regular  and  symmetri- 
cal ;  and  at  least  one  instance  of  the  kind  is  recorded  where  all 
the  stamens  but  one  have  been  restored  and  in  their  normal  posi- 
tions.    From  the  study  of  such  instances  it  may  be  concluded 
that  the  spade-shaped  body  of  this  flower  is  actually  one  of  the 
outer  whorl  of  stamens  and  really  represents  the  hypertrophied 
connective  of  one  of  the  anthers,  and  that  the  other  two  stamens 
belong  to  the  second  or  inner  whorl,  the  third  having  disappeared 
or  perhaps  coalesced  with  the  lower  petal  to  form  the  labellum. 


192  LABORATORY    EXERCISES   IN   BOTANY. 

(5)  The   Gyncedum. — This  also    has   become  strongly  altered 
from  that  of  the  mouocotyl  type,  but  the  type  is  still  recognizable 
through  the  modifications.     The  ovary  shows  exteriorly  a  three- 
lobed  character  ;  the  stigma,  though  irregular,  is  three-lobed  ;  and 
a  cross-section  of  the  ovary  shows  three  marginal  placentae, — all 
indicating  that  the  pistil  is  composed  of   three  united  carpels. 
Besides  the  irregular  stigma,  the  bent  style,  and  the  curved  ovary, 
there  is  another  irregularity  which  merits  attention — namely,  the 
twist  in  the  ovary.     Close  observation  shows  that  it  is  twisted 
through  half  a  revolution,  thus  inverting  the  flower.     The  la- 
bellum,  therefore,  which  appears  to  be  the  lower  petal,  is  really 
the  upper  one ;  and,  similarly,  the  spade-shaped  body  represents 
the  lower  stamen  of  the  outer  whorl,  instead  of  the  upper  one. 

(6)  The  ground  plan  of  the  flower,  therefore,  is  as  represented 
in  Figure  2  (PL  XXIX.),  the  dot  indicating  which  is  the  real 
upper  side  of  the  flower,  and  the  organs  with  dotted  outlines  rep- 
resenting the  floral  parts  that  have  disappeared. 

(7)  The  Pollination. — The  explanation  for  these  strange  irreg- 
ularities and  dissymmetries  is  that  the  flower  has  become  grad- 
ually modified  in  relation  to  its  insect  visitors.     The  mode  of 
cross-fertilization  in  this  flower  affords  an  interesting  study,  and 
the  process  is  briefly  outlined  as  follows :  The  insect,  usually  a 
bee  or  a  wasp,  pushes  its  way  through  the  closed   slit  in  the 
labellum  at  e,  and,  once  inside,  proceeds  to  the  base,  where  is 
secreted   the  nectar,  the  object  of  the   visit;   in   doing  this  the 
insect  necessarily  passes  under  and  rubs  against  the  stigma,  any 
pollen  which  may  have  adhered  to  the  back  of  the  insect  from  a 
visit  to  another  flower  being  deposited  upon  the  stigma ;  having 
sipped  the  nectar,  the  insect  emerges  from  the  labellum,  not  by 
retracing  the  path  pursued  in  entering,  but,  seeing  light  under 
the  spade-shaped  body  at  c,  by  forcing  a  way  out  there;  in   so 
doing  the  insect  rubs  its  back  against  one  of  the  two  anthers, 
and  carries  the  pollen  away  to  the  next  flower  visited. 


FLOWERS   OF   MONOCOTYLS. 


193 


PLATE  XXVIII.,  FIGS.  1,  2.— Flowers  of  Narcissus  poeticus  in  different  positions  (% 
natural  size). 

FIG.  3.— Vertical  Section  of  one  of  the  Flowers,  showing,  a,  corona ;  6,  one  of  the 
petals ;  c,  one  of  the  stamens ;  d,  the  stigma ;  e,  an  anther ;  /,  the  style ;  g,  the  ovary ;  ft, 
the  receptacle ;  and  i,  the  peduncle. 

FIG.  4.— Ground  Plan  of  Narcissus  Flower:  a,  sepal;  6,  petal;  c,  stamen;  d,  ovary. 
13 


FLOWERS    OF    MONOCOTYLS. 


195 


a 


PLATE  XXIX.,  FIG.  1.— Two  Plants  of  Cypripedium  acaule  (%  natural  size),  slewing 
flowers  in  different  positions  :  o,  sepal ;  b,  base  of  column  ;  c,  opening  from  which  insect 
emerges ;  d,  lateral  petal ;  e,  slit  through  which  insect  enters ;  /,  ovary ;  g,  upper  two 
united  into  one. 


FIG.  2.— Ground  Plan  of  one  of  the  Flowers:  a,  upper  two  sepals  united  into  one;  b, 
labellum  ;  c,  a  stamen  ;  d,  spade-shaped  body,  an  abortive  stamen. 


EXERCISE  XXV. 

STUDY  OF  THE  INFLORESCENCE  OF  AN  ABERRANT  MONO- 
COTYL,  ONE  OF  THE  ARACEJ2. 

THE  following  are  species  most  of  which  are  not  difficult  to 
procure  in  the  proper  season,  and  which  are  suitable  for  study  : 
the  Indian  Turnip  (Arissema  triphyllum,  Torr.\  the  Green  Dragon 
(Arissema  Dracontium,  Schott.),  the  Arrow  Arum  (Peltandra  Vir- 
ginica,  Kunth),  the  Water  Arum  or  Calla  (Calla  palustris,  _L.),  the 
Calla  Lily  (Richardia  JEthiopica,  Kuntfi),  the  Golden  Club  (Oron- 
tium  aquaticum,  Z/.),  the  Skunk  Cabbage  (Symplocarpus  foetidus, 
Salisb.),  and  the  Sweet  Flag  (Acorus  Calamus,  L.). 

For  the  purposes  of  this  exercise  selection  is  made  of  the  first 
on  the  list,  the  Indian  Turnip.  The  plant  is  very  common  in  low, 
rich  woods  throughout  the  eastern  portion  of  the  United  States 
and  Canada,  where  it  blossoms  in  early  spring.  It  has  a  flattened, 
much  wrinkled  corm  that  may  attain  a  transverse  diameter  of  two 
inches  and  a  vertical  diameter  half  as  great,  and  emits  numerous 
nearly  simple,  adventitious  roots  from  its  upper  margin.  From 
near  the  centre  of  its  upper  surface  rises,  to  the  height  of  six 
inches  or  even  a  foot  or  more,  the  erect,  rather  stout,  cylindrical 
scape.  The  lower  part  is  enveloped  in  alternate  sheathing  scales 
and  the  sheathing  base  of  the  true  leaf  or  leaves.  The  scales  are 
large,  particularly  the  upper  ones,  and  conspicuously  parallel- 
nerved.  The  true  leaves,  one  or  two  in  number,  like  the  scales? 
have  their  origin  in  the  corm.  Besides  the  long  sheath,  which 
completely  surrounds  the  flower-stem,  the  leaf  consists  of  a  rather 
long,  cylindrical  petiole  and  a  ternately-divided  blade.  The  leaf 
deviates  in  structure  from  that  of  the  great  majority  of  mono- 
cotyls  in  being  reticulate  instead  of  nerved.  The  segments  are 
ovate,  entire-margined,  acuminate,  and  have  a  sub-marginal  vein 
running  from  the  base  to  the  apex.  The  whole  plant  is  smooth, 
and  the  watery  juice  is  very  acrid. 

197 


198  LABORATORY    EXERCISES   IN    BOTANY. 

(1)  The  anthotaxy  is  of  that  variety  of  the  indeterminate  type 
which  is  called  the  spadix ;  that  is,  the  florets  of  the  cluster  are 
sessile  and  arranged  along  a  fleshy,  usually  elongated  axis  which  is 
subtended  by  a  conspicuous  and  often  showy  bract  called  the  spathe. 
In  this  instance  the  lower  part  of  the  spadix,  which  is  conical  in 
form,  is  the  only  flower-bearing  part.    The  upper  portion  is  elon- 
gated, smooth,  and  club-shaped.     The  lower  part  of  the  spathe  is 
rolled  into  an  ob-couical  or  nearly  cylindrical  tube  which  nearly 
encloses  the  spadix,  and  the  upper  part  is  flattened,  ovate-lanceo- 
late, and  acuminate,  and  arches  over  the  top  of  the  spadix.     It  is 
more  or  less  ornamented  with  purplish  blotches. 

(2)  The  flowers  are  of  two  kinds,  staminate  and  pistillate,  some- 
times both  borne  on  the  same  spadix  (monoecious),  the  staminate 
above  the  pistillate,  and  sometimes  on  the  spadices  of  different 
plants  of  the  species  (dioecious).     The  floral  envelopes  are  wholly 
wanting. 

(a)  The  staminate  flowers  consist  each  of  a  single  stamen  with 
a  very  short  and  stout  filament  and  a  four-celled  anther,  each  cell 
opening  above  by  a  narrow  chink  or  pore.  The  pollen-grains  are 
spherical  and  studded  with  minute  points. 

(6)  The  pistillate  flowers  are  equally  simple,  consisting  each  of 
a  single  pistil.  This  has  at  its  apex  a  small  sessile  stigma.  The 
ovary  is  rounded  or  faintly  triangular,  one-celled,  and  usually 
about  six-ovuled.  Each  fertilized  pistil  becomes,  when  ripe,  a 
scarlet  berry. 

The  characters  of  the  plant,  it  will  be  observed,  are  somewhat 
contradictory.  If  a  cross-section  of  the  corm  or  of  the  scape  be 
made,  the  vasal  bundles  will  be  found  scattered  as  in  monocotyls, 
while  the  leaves  have  the  netted  venation  of  dicotyls  and  the 
flowers  are  so  reduced  that  from  these  alone  it  would  be  impos- 
sible to  decide  to  which  of  the  two  groups  the  plant  belongs. 
But  much  light  may  be  derived  from  the  comparison  of  this  with 
related  plants.  In  the  Calla  Lily,  for  example,  the  pistil  is  dis- 
tinctly three-car peled,  as  shown  on  Plate  XXX.  (Fig.  4,  a  and 
b).  This  and  other  facts  derived  from  the  study  of  manifestly  re- 
lated plants  lead  to  the  conclusion  that  the  one-celled  pistil  of 
Arissema  is  really  three-carpelcd,  though  the  fusion  is  so  complete 
that  the  traces  of  its  compound  character  him-  nearly  disappeared. 

In  some  other  members  of  the  order,  as  in  Oroutium,  there  is 


STUDY   OF   AN   ABERRANT   MONOCOTYL.  199 

a  perianth  of  six  pieces,  as  in  most  monocotyls;  so  there  can  be 
no  doubt  that  Arisaema  is  really  a  monocotyl,  though  by  the 
reduction  of  its  parts  it  has  become  very  aberrant  from  its  type. 
This  instance  illustrates  the  value  of  comparison  in  determining 
the  relationships  of  a  species. 

Another  thing  that  should  be  learned  from  the  study  of  this 
plant  is  that  hard  and  fast  lines  cannot  be  drawn  even  between 
two  groups  usually  so  distinct  as  monocotyls  and  dicotyls,  much 
less  between  smaller  and  more  nearly  related  groups.  Nearly 
always  dicotyls  have  net-veined  leaves  and  monocotyls  nerved 
ones,  but  here  is  a  monocotyl  whose  leaves  possess  the  net-veined 
character  of  dicotyls.  It  is  in  some  respects  on  the  border-line — 
a  connecting-link — between  two  great  sub-classes.  Connecting- 
links  between  species,  genera,  and  even  orders,  are,  contrary  to 
the  popular  supposition,  far  from  being  rare  in  the  vegetable 
kingdom. 


STUDY    OF    AN    ABERRANT    MONOCOTYL. 


201 


PLATE  XXX.,  FIG.  1.— Plant  of  Arissema  triphyllum  (about  f  natural  size). 

FIG.  2.— Staminate  spadix  with  spathe  cut  away  to  show  the  flowers :  a,  naked  portion 
of  spadix ;  b,  a  staminate  flower ;  c,  an  enlarged  view  of  upper  side  of  a  stamen ;  d,  a 
lateral  view  of  the  same ;  e,  two  pollen-grains  strongly  magnified. 

FIG.  3.— Spadix  of  another  flower  of  the  same  species  in  which  only  a  few  staminate 
flowers  are  present,  but  numerous  pistillate  ones  :  a,  staminate  flower  ;  b,  pistillate  flower; 
c,  one  of  tbe  pistils  enlarged  :  d,  the  same  in  longitudinal  section,  showing  the  six  orthot- 
ropous  ovules  arising  from  a  basal  placenta. 

FIG.  4.— Sections  of  Ovary  of  Calla  Lily :  a,  of  lower  part,  where  three  placentae  meet  in 
the  centre ;  and  b,  of  the  upper  part,  where  the  placentation  is  marginal. 


FOKM   FOB  THE  STUDY  OF  FLOWERS. 


I.  ANTHOTAXY. 

III.  KINDS  OF  ORGANS  PRES 

3.  Petaloid. 

1.  Indeterminate. 

ENT. 

4.  Deciduous. 

(I)  Solitary. 

1.  Bracts. 

5.  Persistent. 

(2j  Raceme. 
(3)  Compound     raceme 
or  panicle. 

2.  Bracteoles. 
3.  Involucre. 
4.  Involucel. 

IX.  INVOLUCRE. 
1.  Herbaceous. 

(4)  Corymb. 

5.  Epicalyx. 

2.  Scarious. 

(5)  Compound  corymb. 
(6)  Umbel. 

6.  Torus. 
7.  Calyx. 

3.  Sacrious-tipped. 
4.  Scarious-margined. 

(7)  Compound  umbel. 
(8)  Spike. 

8.  Corolla. 
9.  Nectaries. 

5.  One-rowed. 
6.  Two-rowed. 

(9)  Compound  spike. 
(10)  Head. 

10.  Stamens. 
11.  Staminodes. 

7.  Imbricated  in  several 

rows. 

(11)  Spadix. 

12.  Pistils. 

X.  TORUS. 

(12)  Catkin. 

IV.  NUMERICAL  PLAN. 

1.  Flat. 

'2.  Determinate. 

1.  Monomerous. 

2.  Convex. 

(1)  Solitary. 
(2)  Cyme. 
(3)  Compound  cyme. 
(4)  Fascicle. 
(5)  Glomerule. 

2.  Dimerous. 
3.  Trimerous. 
4.  Tetramerous. 
5.  Pentamerous. 
6.  Hexamerous. 

3.  Hemispherical. 
4.  Conical. 
5.  Concave. 
6.  Hollow. 

• 

(6)  Scorpioid  cyme. 
(7)  Helicoid  cyme. 
(8)  Verticillaster. 
3  Mixed 

7.  Heptamerous. 
8.  Octamerous. 
9.  Polymerous. 

XI.  CALYX. 
1.  Insertion. 
(1)  Hypogynous. 

(1)  Mixed  panicle. 
(2)  Thyrsus. 
(8)  Spiked  verticillaster. 

V.  SYMMETRY. 
1.  Symmetrical. 
2.  Unsymmetrical  calyx. 

(2)  Perigynous. 
(3)  Epigynous. 
2.  Chorisepalous. 

(4)  Cymed  heads. 

3.              "           corolla. 

(1)  Sepals  : 

(5)  Corymbed  cymes. 

4.                           stamens. 
5.                           pistils. 

Sessile. 
Unguiculate. 

Cfl.lc8.rRt6 

II.  PREFLORATIOX. 

VI.  REGULARITY. 

Filiform. 

1.  Individual  piece. 

I.  Regular. 

Linear. 

(1)  Not  bent  or  folded. 

2.  Irregular  calyx. 

Oblong. 

(2)  Inflexed. 

3.         "          corolla. 

Clavate. 

(8)  Reflexed. 

4.         "          stamens. 

Elliptical. 

(4)  Conduplicate. 

VII.  FERTILIZATION. 

Lanceolate. 

(5)  Convolute. 
(6)  Circinate. 
(7)  Plicate. 
(8)  Involute. 
(9)  Revolute. 
2.  Relative  position  of  pieces. 
(1)  Valvate  series. 
a.  Valvate. 
b.  Induplicate-valvate. 
c.  Reduplicate-valvate. 
d.  Involute-  valvate. 
e.  Revolute-valvate. 

1.  Autogamous. 
2.  Cleistogamous. 
3.  Allogamous. 
(1)  Anemophilous. 
a.  Monoecious. 
b.  Dioecious. 
c.  Hermaphrodite, 
(a)  Protandrous. 
(b)  Protogynous. 
(2)  Entomophilous. 
a.  Monoecious. 

Oblanceolate. 
Ovate. 
Obovate. 
Orbicular. 
Emarginate. 
Cordate. 
Obcordate. 
Saccate. 
Entire. 
Toothed. 
Fringed. 
Herbaceous. 

(2)  Imbricate  series. 

b.  Dioecious. 

Scarious. 

a.  Imbricate. 

c.  Hermaphrodite. 

Petaloid. 

&.  Quincuncial. 
c.  Vexillary. 
d.  Equitant. 
e.  Half-equitant. 
/.  Triquetrous. 
3.  Gamophyllous  organs. 

(a)  Protandrous. 
(6)  Protogynous. 
(c)  Dimorphous. 
(d)  Trimorphous. 
(e)  Irregularity. 
(/)  Special     adapta- 

Length. 
3.  Gamosepalous. 
(1)  Tubular. 
(2)  Rotate. 
(3)  Campanulate. 
(4)  Infundibuliform. 

(1)  Contorted. 

tions. 

(5)  Hypocrateriform. 

(2)  Plicate. 

VIII.  BRACTS. 

(6)  Urceolate. 

(3)  Supervolute. 

1.  Herbaceous. 

(7)  Globose. 

2.  Scarious. 

(8)  Inflated. 

FORM   FOE  THE  STUDY  OF  FLOWERS  (CONTINUED). 


(9)  Bilabiate. 

(9)  Bilabiate. 

b.  Filiform. 

(10)  Saccate. 

(10)  Personate. 

c.  Awl-shaped. 

(11)  Calcarate. 

(11)  Ringent. 

d.  Clavate. 

(12)  Herbaceous. 

(12)  Ligulate. 

e.  Bearded. 

(13)  Petal  oid. 

(13j  Saccate. 

/.  Appendaged. 

(14)  Length  of  tube. 

(14)  Calcarate. 

g.  Petaloid. 

(15)  Limb. 

(15)  Coronate. 

(2)  Anthers. 

a.   Entire. 

(16)  Length  of  tube. 

a.  Insertion. 

b.   Toothed. 

(17)  Limb. 

(a)  Sessile. 

c.    Fringed. 

a.  Entire. 

(b)  Introrse. 

d.  Crisped. 

b.    Toothed. 

(c)  Extrorse. 

e.    Lobed. 

c.    Fringed. 

(d)  Adnate. 

/.   Parted. 

d.  Crispate. 

(e)  Innate. 

g.    Divided. 

e.    Lobed. 

(/)  Versatile. 

(16)  Number   of   compo- 

/. Parted. 

b.  Dehiseence. 

nent  sepals. 

g.   Divided. 

(a)  Longitudinal. 

4.  Duration. 

(18)  Color. 

(6)  Transverse. 

(1)  Caducous. 

(19)  Number   of   compo- 

(c) Valvular. 

(2)  Deciduous. 

nent  petals. 

(d)  Porous. 

(3)  Withering. 

4.  Duration. 

(e)  Irregular. 

(4)  Persistent. 

(1)  Caducous. 

c.  Structure. 

(5)  Accrescent. 

(2)  Deciduous. 

(a)  Unilocular. 

(3)  Withering. 

(b)  Bilocular. 

XII.  COROLLA. 

(4)  Persistent. 

(c)  Quadrilocular. 

1.  Insertion. 

(d)  Dimidiate. 

(1)  Hypogynous. 

XIII.  ANDRCECIUM. 

(e)  Appendaged. 

(2)  Perigynous. 

1.  Number  of  stamens. 

d.  Connective. 

(3)  Epigynous. 

(1)  Monandrous. 

(a)  Narrow. 

2.  Choripetalous. 

(2)  Diandrous. 

(b)  Broad. 

(1)  Petals: 

(3)  Triandrous. 

(c)  Caudate. 

Sessile. 

(4)  Tetrandrous. 

(3)  Pollen. 

Unguiculate. 

(5)  Pentandrous. 

d.  Powdery. 

Coronate. 

(6)  Hexandrous. 

6.  Adhesive. 

Calcarate. 

(7)  Heptandrous. 

c.  In    masses    or    pol- 

Filiform. 

(8)  Octandrous. 

linia. 

Clavate. 

(9)  Enneandrous. 

Linear. 

(10)  Decandrous. 

Oblong. 

(11)  Endodecandrous. 

XIV.  GYNGECIUM. 

Elliptical. 

(12)  Duodecandrous. 

1.  Kind. 

Lanceolate. 

(13)  Polyandrous. 

(1)  Gymnospermous. 

Oblanceolate. 

2.  Grouping  of  stamens. 

(2)  Angiospermous. 

Ovate. 

(1)  Distinct. 

(3)  Apocarpous. 

Obovate. 

(2)  Monadelphous. 

(4)  Syncarpous. 

Orbicular. 

(3)  Diadelphous.' 

2.  Apocarpous  gyncecium. 

Emarginate. 

(4)  Triadelphous. 

(1)  Number  of  carpels. 

Obcordate. 

(5)  Polyadelphous. 

3.  Syncarpous  gynvecium. 

Cordate. 

(6)  Syngenesious. 

(1)  Number    of     compo- 

Entire. 

(7)  Didynamous. 

nent  carpels. 

Toothed. 

(8)  Tetradynamous. 

(2)  Degrees  of  union. 

Fringed. 

3.  Insertion  of  stamens. 

a.  Ovaries  partly  unit- 

Color. 

(1)  Hypogynous. 

ed. 

Length. 

(2)  Perigynous. 

6.  Ovaries  wholly  unit- 

Number. 

(3)  Epigynoun. 

ed. 

3.  Gamopetalous. 

(4)  Epipetalous. 

c.  Ovaries  and  part  of 

(1)  Tubular. 

(5)  Gynandrous. 

styles  united. 

(2)  Rotate. 

(6)  Included. 

d.  Ovaries    and    styles 

(3)  Campanulate. 

(7)  Protruding. 

united. 

(4)  Infundibuliform. 

(8)  Equal  in  length. 

e.  Stigmas  only  united. 

(5)  Hypocrateriform. 

(9)  Unequal  in  length. 

4.  Parts. 

(6)  Urceolate. 

4.  Parts. 

1.  Ovary. 

(7)  Globose. 

(1)  Filament. 

2.  Style. 

(8)  Inflated. 

a.  Wanting. 

3.  Stigma. 

FOKM   FOE  THE  STUDY  OF  FLOWERS  (CONTINUED). 


5.  Insertion. 

6.  Lateral. 

(3)  Structure. 

1.  Ovary  superior. 

c.  Basal. 

a.  Atropous. 

2.      "      half-superior. 

(5)  Form. 

b.  Campylotropous. 

3.       "       inferior. 

a.  Filiform. 

c.  Amphitropous. 

4.      "      stipitate. 

b.  Clavate. 

d.  Anatropous. 

5.      "      sessile. 

c.  Prismatic. 

6.  Ovary. 

d.  Awl-shaped. 

XV.  TASTE. 

(1)  Shape. 

e.  Cylindrical. 

a.  Cylindrical. 

/.  Short. 

1.  Insipid. 

6.  Oblong. 

g.  Thick. 

2.  Bland. 

c.  Ovoid. 

h.  Petaloid. 

3.  Sweet. 

d.  Conical. 
€.  Globose. 

i.  Persistent. 
j.  Deciduous. 

4.  Bitter. 
5.  Mucilaginous. 

/.  Flattened. 

8.  Stigmas. 

6.  Pungent. 

(a)  In  a  vertical  di- 

(1) Number. 

7.  Acrid. 

rection. 

(2)  Sessile. 

8.  Warm. 

(b)  In    a    transverse 
direction. 

(3)  Capitate. 
(4)  Convex. 

9.  Burning. 
10.  Cooling. 

g.  Lobate. 

(5)  Flat. 

11.  Astringent. 

h.  Alate. 

(6)  Conical. 

12.  Nauseous. 

i.  Curved. 

(7)  Concave. 

13.  Prickling. 

j.  Contorted. 
(2)  Structure. 

(8)  Beaked. 
(9)  Filamentous. 

14.  Saline. 
15.  Alkaline. 

a.  Unilocular. 

(10)  Plumose. 

16.  Acidulous. 

b.  Bilocular. 

(11)  Radiate. 

c.  Trilocular. 

(12)  Decurrent. 

XVI.  ODOR. 

d.  Quadrilocular. 

(13)  Lobed. 

1.  Odorless. 

e.  Quinquelocular. 

(14)  Parted. 

2.  Faint. 

/.  Sexilocular. 

(15)  Peltate. 

3.  Agreeable. 

g.  Septilocular. 

(16)  Fringed. 

4.  Aromatic. 

h.  Multilocular. 

.9.  Ovules. 

5.  Mint-like. 

(3)  Placentation. 

(I)  Number. 

6.  Balsamic. 

a.  Marginal. 

a.  One  in  each  cell. 

7.  Camphoraceous. 

b.  Basilar. 

6.  Two  in  each  cell. 

8.  Terebinthinous. 

o.  Axillary. 

c.  Several  in  each  cell. 

9.  Pungent. 

d.  Parietal. 

d.  Many-ovuled. 

10.  Musky. 

7.  Styles. 

(2)  Position. 

11.  Disagreeable. 

(1)  Number. 

a.  Erect. 

12.  Irritating. 

(2)  Distinct. 

b.  Ascending. 

13.  Nauseous. 

(3)  Partly  united. 

c.  Horizontal. 

14.  Narcotic. 

(4)  Position. 

d.  Pendulous. 

15.  Putrid. 

a.  Terminal. 

e.  Suspended. 

16.  Fetid. 

EXERCISE  XXVI. 

STUDY  OF  FEUITS:   SOME  APOCAEPOUS  FKUITS. 

SELECTIONS  may  be  made  from  fruits  of  the  following  plants : 
the  Buttercup  (Ranunculus  bulbosus,  Z.),  the  Marsh  Marigold 
(Caltha  palustris,  L.\  the  Goldthread  (Coptis  trifolia,  8alisb.), 
the  Moouseed  (Menispermum  Canadense,  L.\  the  Common  Pea 
(Pisum  sativum,  L.)9  the  Scarlet  Runner  (Phaseolus  multifloriis, 
Willd.\  the  Cultivated  Cherry  (Primus  avium,  L.),  the  Peach 
(Primus  Persica,  L.\  the  Common  Plum  (Primus  domestica,  L.), 
and  the  Common  Milkweed  (Asclepias  cornuti,  Decaisne). 

From  these  are  taken  for  the  present  purpose  two  which  differ 
from  each  other  quite  widely — the  fruit  of  the  Common  Pea  and 
that  of  the  Cultivated  Cherry. 

A  fruit  may  be  defined  as  a  ripened  pistil.  It  is  nothing  more, 
in  most  cases,  than  a  hollow  vessel  or  pericarp  containing  in  its 
interior  a  seed  or  seeds.  This  ripened  pistil,  like  that  of  the  im- 
mature one  in  the  flower  from  which  it  is  derived,  may  represent  a 
single  leaf  or  a  cluster  of  united  leaves;  that  is,  it  may  be  either 
apocarpous  or  syncarpous.  It  usually  follows  the  structure  of  the 
pistil  also  in  its  placentation  and  in  the  number  of  its  loculi, 
though  rarely  both  undergo  changes  in  development.  The  text- 
ure of  the  pericarp  shows  great  variety  in  its  structure  in  dif- 
ferent fruits  :  it  is  sometimes  thick  and  sometimes  thin ;  some- 
times hard  and  sometimes  soft;  sometimes  hard  exteriorly  and 
soft  interiorly,  and  sometimes  the  reverse ;  sometimes  smooth 
exteriorly  and  sometimes  roughened,  hairy,  spinose,  alate,  or 
papillose ;  and  sometimes  dehiscent  and  sometimes  indehiscent. 
Most  of  the  different  forms  the  pericarp  assumes  have  reference 
in  some  way  to  the  modes  of  dispersion — by  the  wind,  by  ani- 
mals, or  by  some  other  agency. 

But  fruits  are  often  something  more  than  single  ripened  pistils : 
they  may  consist  of  a  cluster  of  distinct  pistils  which  still  remain 

203 


204  LABORATORY   EXERCISES   IN   BOTANY. 

attached  to  the  common  receptacle,  as  in  the  Blackberry,  Anemone, 
and  Mulberry,  and  these  clusters  may  be  the  product  of  a  single 
flower,  as  in  the  first  two  examples  mentioned,  or  the  product  of 
a  flower-cluster,  as  in  the  last  and  in  the  Pineapple.  In  the  for- 
mer case  they  are  called  aggregated  fruits,  in  the  latter  multi- 
ple ones.  Moreover,  in  another  way  a  fruit  is  not  always  simply 
a  ripened  pistil.  Take  the  Strawberry  as  an  example.  Here  the 
fruits  proper  are  the  small,  seed-like  bodies  (achenia)  sprinkled 
over  the  conical,  fleshy,  scarlet  pulp,  which  is  really  the  greatly 
enlarged  receptacle.  The  whole  is  called  a  fruit ;  it  is  an  aggre- 
gated fruit  with  an  accessory  receptacle.  So  also  there  are  fruits 
in  which  the  persistent  calyx  constitutes  a  conspicuous  part,  or 
fruits  with  an  accessory  calyx. 

With  this  preface,  let  us  proceed  to  the  study  of — 

I.  THE  FRUIT  OF  THE  PEA. — This  fruit  is  commonly  called 
a  pod,  and  in  cookery  it  is  treated  as  a  vegetable,  but  in  the  botan- 
ical sense  it  is  as  much  a  fruit  as  is  an  apple  or  a  grape.  In  mak- 
ing a  study  of  it,  it  would  be  well  to  have  before  the  student  both 
ripe  and  fully-grown  but  unripe  pods. 

(1)  External  Characteristics. — Distinction  must  first  be  made 
between  the  base  and  the  apex  of  the  fruit.  At  the  former 
there  will  be  found,  when  the  fruit  is  ripe,  the  withered  remains 
of  the  calyx.  It  is  therefore  a  superior  fruit.  At  the  apex  will 
be  seen  the  withered  base  or  scar  of  the  style,  which,  having 
performed  its  functions  in  the  flower,  has  partially  or  wholly 
disappeared  along  with  the  stigma.  In  some  kinds  of  fruits 
both  persist  and  constitute  a  part  of  the  ripe  fruit. 

The  pericarp  of  the  ripe  Pea  fruit  is  dry,  rather  thin — that  is, 
of  about  the  thickness  of  cardboard — and  rather  hard  and  elastic. 
If  it  has  not  yet  dehisced,  there  may  be  observed  on  opposite 
edges,  and  running  from  base  to  apex,  two  sutures — one,  usually 
that  on  the  straighter  edge,  called  the  ventral,  and  the  other  the 
dorsal  suture.  When  the  pod  is  fully  ripe  slight  pressure  will 
cause  its  dehiscence  along  these  sutures,  and  at  the  same  time  the 
two  valves  become  somewhat  twisted.  These  movements  are  the 
result  of  unequal  drying,  which  produces  a  strain  upon  the  peri- 
carp, and  it  needs  only  a  touch  or  a  slight  blow  to  cause  the  struc- 
ture to  yield  along  its  weaker  portions,  which  in  this  case  arc  the 
sutures.  As  a  result  of  the  dehisceuce  the  seeds  are  usually  thrown 


STUDY   OF   SOME   APOCARPOUS    FRUITS.  205 

out,  not  merely  dropped  out.  Dispersion  of  the  species  is  thus 
facilitated. 

(2)  Internal  Structure. — Selecting  a  fruit  which  is  fully  grown, 
but  not  yet  ripe,  it  is  opened  carefully  along  its  sutures.  The 
seeds  will  be  found  arranged  as  shown  on  Plate  XXXI. 
(Fig.  2).  They  are  borne  along  one  suture — the  ventral — but 
not  along  the  other.  Moreover,  the  seeds  are  attached  alternately, 
first  on  one  edge  and  then  on  the  other.  In  fact,  these  edges  are 
the  infolded  margins  of  the  carpellary  leaf,  the  other  suture  rep- 
resenting the  midrib  of  the  leaf.  The  placentation  is  marginal 
and  the  fruit  is  apocarpous.  A.  dry  apocarpous  fruit  which  de- 
hisces into  two  valves  along  its  dorsal  and  ventral  sutures  is 
technically  called  a  legume.  Fruits  of  this  type  are  common  in 
the  Pulse  family  of  plants,  hence  the  name  Leguminosse. 

II.  THE  FRUIT  OF  THE  CHERRY. — This  fruit  usually  has  the 
form  of  an  oblate  spheroid  with  a  slight  concavity  at  the  basal 
end  into  which  the  end  of  the  peduncle  fits,  and  sometimes  a 
shallow  groove  running  from  base  to  apex  along  one  side.  In 
this,  as  in  the  example  just  studied,  one  sees  by  observing  the 
base  that  the  calyx  forms  no  part  of  the  fruit,  which  is  therefore 
superior.  At  the  apex  is  found  a  minute  scar  marking  the  posi- 
tion of  the  style,  which  here  also  has  withered  and  disappeared. 

(1)  The  pericarp  is  altogether  different  in  its  texture  from  that 
of  the  Pea,  and  it  does  not  dehisce  when  ripe.     It  has,  in  fact,  in 
its  development  from  the  pistil  become  differentiated  into  two 
portions  widely  unlike  in  texture :  the  outer,  called  the  sarcocarp, 
is  thick  and  juicy,  constituting  the  edible  parfc  of  the  fruit,  while 
the  inner  part,  called  the  pit  or  putamen,  is  developed  into  a  hard, 
bony  enclosure  for  the  seed. 

(2)  Evidence  that  the  Fruit  is  Apocarpous. — Owing  to  the  great 
thickening  of  the  pericarp  and  the  succulency  of  its  outer  part,  it 
is  more  difficult  to  demonstrate  from  the  study  of  the  fruit  alone 
that  it  is  composed  of  a  single  modified  leaf  than  it  is  in  the 
-case  of  the  Pea,  for  the  dorsal  and  ventral  sutures  are  seldom 
distinctly  traceable  from  the  outside.     The  shallow  groove  often 
seen  on  the  outside,  running  lengthwise  of  the  fruit,  is,  however, 
significant.     It  is  really  the  ventral  suture.     Sometimes,  though 
rarely,  the  dorsal  suture  is  traceable  as  a  faint  ridge  on  the  oppo- 
site side.     The  oue-carpeled  character,  however,  is  evident  if  the 


LABORATORY    EXERCISES   IN   BOTANY. 

pi.stil  of  the  flower  be  studied.  Moreover,  the  sutures,  both  dor- 
sal and  ventral,  are  more  or  less  distinctly  traceable  as  ridges  on 
the  pit,  running  from  base  to  apex  on  opposite  sides. 

(3)  Internal  Structure. — If  the  pit  be  divided  transversely,  there 
will  usually  be  found  but  a  single  seed ;  but  if  a  similar  section 
of  the  ovary  of  the  flower  be  made,  there  will  be  found  two 
ovules,  these  being  attached  side  by  side,  adjacent  to  the  ventral 
suture,  as  in  the  Pea.  In  fact,  in  rare  instances  both  ovules 
develop  and  the  pit  is  then  two-seeded. 

A  fruit  of  this  type — an  indehiscent  fruit  whose  pericarp  is 
differentiated  into  sarcocarp  and  hard  endocarp — is  technically 
called  a  drupe.  This  sort  of  fruit  may  be  one-carpeled,  as  in 
the  present  instance,  or  it  may  be  two-  or  more  carpeled. 

The  question  naturally  arises,  Why  should  two  pistils  con- 
structed on  the  same  essential  plan  develop  into  fruits  so  widely 
different  in  appearance  and  structure  as  those  of  the  Pea  and  the 
Cherry?  The  question  can  partially  be  answered  by  supposing 
them  to  be  adapted  in  different  ways  to  dispersion.  The  seeds 
of  the  Pea,  though  edible,  are  not  protected  from  animal  enemies, 
and  for  this  reason,  perhaps,  are  produced  in  greater  numbers  in 
the  fruit.  A  sufficient  number  of  the  seeds  scattered  by  the  de- 
hiscence  of  the  pods  will  usually  elude  the  observation  of  animals 
to  serve  the  purpose  of  reproduction. 

The  sarcocarp  of  the  Cherry  was  manifestly  fitted  to  be  eaten  ; 
it  has  an  attractive  color  and  a  pleasant  taste,  but  the  seed  at  the 
same  time  is  protected  from  destruction  by  its  bony  enclosure. 
Most  of  the  smaller  animals  will  reject  the  pit,  but  in  devouring 
the  rest  they  are  liable  to  convey  the  protected  seed  to  a  distance 
from  the  parent  tree.  Some  few  seeds,  at  least,  will  probably  be 
left  in  positions  favorable  for  germination  and  growth  into  trees. 
None  the  less  is  the  dispersion  of  the  species  promoted  if  the  fruits 
are  devoured  whole  by  larger  animals,  for  the  bony  pit  in  this  case 
will  usually  pn.tcct  the  seed  from  digestion  ;  it  will,  in  fact,  often 
pass  through  the  alimentary  canal  only  the  better  prepared  for  u<-r- 
mination.  There  is  every  reason  for  believing  that  the  qualities 
which  render  the  Cherry,  the  Peach,  the  Plum,  and  other  similar 
finite  desirable  for  fbbd  have  been  gradually  developed  in  the  course 
of  a-_i-es  by  the  selection  exercised  by  frugivorotis  animals.  All 
species  vary  more  or  less,  and  those  varieties  whose  fruits  were 


STUDY   OF   SOME   APOCARPOUS    FRUITS.  207 

most  easily  seen  by  animals  and  most  palatable  to  them,  and  at 
the  same  time  possessed  the  most  thoroughly  protected  seeds, 
would  be  most  likely  to  survive  in  the  struggle  for  existence  and 
to  perpetuate  their  kind.  So,  in  course  of  time,  thick-walled,  lus- 
cious, and  relatively  large  and  showy  fruits  have  been  developed 
from  forms  that,  from  the  standpoint  of  the  modern  epicure, 
would  be  wholly  undesirable.  Animals,  in  fact,  have  been  doing 
blindly  what  the  horticulturist  in  recent  times  has  been  accom- 
plishing with  greater  intelligence  and  more  rapidity. 

(4)  The  seed  in  the  Cherry  is  so  large  that  its  structure  may 
easily  be  determined  with  the  simple  microscope.  In  the  first 
place,  it  will  be  observed  that  the  seed  is  pendulous,  or  points 
obliquely  downward  toward  the  base  of  the  fruit ;  it  is  also 
anatropouSj  having  a  raphe  running  nearly  the  whole  length  of 
one  edge,  and  the  hilum  and  micropyle  located  adjacent  to  each 
other  at  the  end  opposite  the  chalaza. 

Removing  the  thin  coats,  it  will  be  seen  that  the  whole  interior 
consists  of  embryo.  The  seed  is  without  a  food-supply  not  a  part 
of  the  embryo,  or,  as  the  botanist  expresses  it,  is  exalbuminous. 
The  embryo  is  also  straight  and  has  two  large,  fleshy  cotyledons 
with  convex  exterior  faces  and  flat  interior  ones,  a  small  caulicle 
tipped  with  a  minute  radicle,  and  between  the  bases  of  the  cotyle- 
dons a  minute  plumule.  It  is,  in  fact,  a  quite  typical  dicotyledo- 
nous embryo. 

If  the  structure  of  one  of  the  seeds  taken  from  the  pea-pod  be 
compared  with  the  seed  just  observed,  there  will  be  found  a  close 
resemblance  in  all  essential  respects.  Both  seeds  are  exalbuminous, 
both  are  anatropous,  both  are  dicotyledonous,  and  both  have  em- 
bryos with  excessively  thickened  cotyledons.  The  most  conspic- 
uous difference  is  the  fact  that  in  the  Pea  the  embryo  is  not  straight, 
but  the  caulicle  is  bent  up  against  the  edges  of  the  cotyledons. 


STUDY   OF   SOME   APOCARPOUS   FRUITS. 


209 


PLATE  XXXI.,  FIG.  1.— Fruit  of  Pea :  a,  withered  calyx  at  base  of  fruit;  6,  relic  of 
style  ;  c,  ventral  suture ;  d,  dorsal  suture. 

FIG.  2.— Young  Fruit  opened  to  show  placentation. 
(Both  figures  about  %  natural  size.) 

FIG.  3.— Fruit  of  Cherry  (about  %  natural  size). 

FIG.  4.— The  same  in  Vertical  Section  through  Sarcocarp:  a,  concave  base,  showing 
attachment  to  peduncle  and  scar  of  calyx;  6,  sarcocarp;  c,  endocarp  or  putamen. 

FIG.  5.— Transverse  Section  through  the  middle  of  the  Fruit:  a,  sarcocarp;  6,  endo- 
carp ;  c,  one  of  the  cotyledons  of  the  embryo. 

FIG.  6.— The  Putamen  (somewhat  enlarged):  a,  the  basal  end;  b,  the  apex;  c,  hilum 
of  seed ;  and  d,  the  embryo. 

14 


EXERCISE  XXVII. 

STUDY  OF  FKUITS :   SOME  SYNCAKPOUS  FKUITS. 

THE  following  are  dehiscent  kinds  of  fruits,  of  common  occur- 
rence, from  which  studies  may  be  made :  the  Opium  Poppy  (Pa- 
paver  somniferum,  L.\  the  Celandine  (Chelidouium  majus,  L.\ 
the  Black  Mustard  (Brassica  nigra,  Koch),  the  Common  Blue  Violet 
(Viola  palmata,  L.),  the  Corn  Cockle  (Lychnis  Githago,  Lam.),  the 
Shrubby  Mallow  (Hibiscus  Syriacus,  L.),  the  Coriander  (Corian- 
drum  sativum,  Willd.),  the  Cranesbill  (Geranium  maculatum,  L.), 
the  Jewel  Weed  (Impatiens  fulva,  Nutt.),  the  Evening  Primrose 
(CEnothera  biennis,  L.),  the  Stramonium  (Datura  Stramonium,  L.\ 
the  Henbane  (Hyoscyamus  uiger,  L.);  the  Tulip  (Tulipa  Gesueriana, 
WiMd.),  the  Blue  Flag  (Iris  versicolor,  L.),  the  Stemless  Lady's 
Slipper  (Cypripedium  acaule,  Ait.),  and  the  Colchicum  (Colchicum 
atitumnale,  L.). 

The  following  plants  afford  easily  obtainable  indehiscent  kinds  : 
the  Common  Apple  (Pyrus  Malus,  L.),  the  Pear  (Pyrus  commuuis, 
L.),  the  Crab-apple  (Pyrus  corouaria,  L.),  the  Service  Berry 
(Amelanchier  Canadensis,  Torr.  and  Gray),  the  Gooseberry 
(Ribes  cynosbati,  L.\  the  Orange  (Citrus  Aurantium,  Willd.), 
the  Lemon  (Citrus  Limonum,  Risso),  the  Cucumber  (Cucumis 
sativus,  L.),  the  Potato  Berry  (Solanum  tuberosum,  L.),  the 
Ground  Cherry  (Physalis  pubescens,  L.),  and  the  Birthwort 
(Trillium  erectum,  L.). 

For  the  first  part  of  this  exercise  the  fruits  of  the  Poppy,  the 
Colchicum,  and  the  Henbane  will  be  studied,  and  they  will  be 
taken  up  in  the  order  named. 

I.  FRUIT  OF  THE  POPPY. — (1)  External  Characteristics. — 
The  Common  or  Opium  Poppy  is  widely  cultivated  for  orna- 
ment and,  in  certain  portions  of  the  world,  as  the  source  of  the 
important  drug  opium.  The  fruits  vary  much  in  size  in  the  dif- 
ferent varieties,  sometimes  attaining  a  length  of  three  inches  or 
more,  but  averaging,  perhaps,  a  length  of  an  inch  and  a  half  to 

211 


212  LABORATORY    EXERCISES    IN    BOTANY. 

two  inches.  The  fruits  are  dry  when  ripe,  obloDg  or  globular, 
more  or  less  ribbed  longitudinally,  and  crowned  by  a  star-shaped, 
many-rayed,  nearly  sessile  stigma.  They  are  somewhat  stalked 
at  the  base,  and  on  the  receptacle  from  which  this  stalk  rises  may 
be  observed  the  scars  of  the  floral  organs  that  have  fallen  away— 
sepals,  petals,  and  stamens.  The  number  of  ribs  and  the  corre- 
sponding number  of  rays  to  the  stigma  are  outside  indications 
which  point  to  the  conclusion  that  the  fruit  is  syncarpous  and 
made  up  of  a  considerable  number  of  carpels.  Further  iudi<-a- 
tions  are  the  little  pores  or  valves  of  dehiscence  which  may  be 
seen  underneath  the  margins  of  the  stigma,  which  correspond  in 
number  with  the  rays  of  the  stigma  and  with  the  ribs  of  the  ovary, 
and  from  which  the  seeds  escape. 

(2)  The  internal  structure,  as  seen  in  cross-section,  confirms  this 
conclusion.     Corresponding  in  number  to  the  ribs  and  stiginatic 
lines  are  marginal  placenta  projecting  well  into  the  cavity  of  the 
fruit.     On  these  placentae  are  borne,  in  double  series,  the  very 
numerous  and  minute  seeds.     In  the  fruit  shown  in  the  illustra- 
tion (PI.  XXXII.  Fig.  2)  there  are  fourteen  placenta?,  and  there- 
fore fourteen  carpels,  but  the  number  will  be  found  to  vary  in 
different  fruits  of  the  species. 

(3)  The  dehiscence,  as  has  been  observed,  is  by  valves  under- 
neath the  stigmas.     It  will  be  well,  in  order  to  understand  the 
nature  of  the  dehiscence,  to  compare  the  different  kinds  that  occur 
in  capsules,  for  a  syncarpous,  dry,  dehiscent  fruit  is  termed  a 
capsule. 

If  a  capsule  is  composed  of  leaf- elements  or  carpels  united  by 
their  edges,  it  would  naturally  be  expected  that  when  dehiscence 
takes  place  to  scatter  the  ripe  seeds,  this  dehiscence  would  occur 
by  the  separation  of  the  carpels  along  the  line  of  their  original 
junction.  This  is,  in  fact,  most  commonly  the  case,  and  dehis- 
cence of  this  kind  is  called  septicidal.  But  there  are  many  in- 
stances where  the  separation  takes  place  along  the  dorsum  or  mid- 
rib of  the  carpel  rather  than  along  the  edges  or  ventral  sutures. 
This  mode  of  dehiscence  is  called  the  loculicidal,  and  it  may  he 
observed  in  the  capsule  of  Blue  Flag.  In  some  capsules  the  de- 
hiscence is  both  septicidal  and  loculicidal,  and  the  capsule  separates 
into  twice  as  many  valves  as  there  are  carpels. 

In  a  third  mode  of  dehiscence  the  separation  takes  place  along 


STUDY    OF   SOME    SYNCARPOUS    FRUITS.  21o 

the  ventral  or  the  dorsal  sutures  or  both,  but  the  valves  break 
away  from  the  placentae,  leaving  the  latter  in  position,  as  in  the 
capsules  of  Cardamom.  This  is  the  septifragal  mode  of  dehiscence. 

In  all  these  types  the  dehiscence  may  be  either  partial  or  com- 
plete, and  it  may  begin  at  the  apex,  the  most  common  mode,  or 
it  may  begin  at  the  base.  Now,  the  mode  of  dehisceuce  that 
occurs  in  the  Poppy  capsule,  though  technically  called  "  porous  " 
or  "  valvular,"  is  really  one  of  partial  septicidal  dehisceuce,  where 
the  opening  begins  at  the  top.  In  the  Campanula  the  dehiscence 
is  valvular,  but  occurs  at  the  base  of  the  capsule. 

Still  another  mode  of  dehiscence  is  seen  in  that  modification  of 
the  capsule  called  the  pyxis,  where  Nature  wholly  ignores  the 
original  sutures,  and  the  opening  is  transverse  or  circumscissile, 
as  in  Portulacca,  the  Marcgravia,  and  the  South  American  Lecy- 
this.  Moreover,  the  dehiscence  in  a  few  instances  takes  place 
without  order  or  by  irregular  rupture  through  any  part  of  the 
pericarp. 

(4)  Provision  for  Dispersion. — The  seeds  of  the  Poppy  are  very 
numerous ;  according  to  M.  C.  Cooke,  a  single  capsule  may  con- 
tain as  many  as  forty  thousand  of  them.  When  ripe  they  become 
detached  from  the  placentaa  and  fall  to  the  bottom  of  the  capsule. 
But  the  valves  of  dehiscence,  as  has  been  seen,  are  at  the  opposite 
end  ;  how  is  it,  then,  that  the  seeds  escape?  It  will  be  observed 
that  the  capsule  when  ripe  is  erect  on  the  end  of  a  dead  but  elas- 
tic stalk.  In  a  stiff  breeze  this  stalk  is  swayed  to  and  fro,  and 
when  the  motion  is  sufficiently  rapid  some  of  the  seeds  are  thrown 
out  of  the  openings  near  the  apex,  and,  being  small  and  light,  are 
caught  up  by  the  wind  and  conveyed  often  to  a  considerable  dis- 
tance from  the  parent  plant.  During  every  wind-storm  the  process 
is  repeated,  until  finally  the  capsules  are  emptied. 

II.  THE  FRUIT  OF  COLCHICUM. — (1)  External  Characteristics. 
—The  brownish  capsule  is  an  inch  or  more  long,  oblong,  abruptly 
pointed,  longitudinally  ribbed  and  furrowed,  and  between  the  ribs 
and  furrows  somewhat  rugose.  By  observing  closely  the  ribs 
and  furrows  there  will  be  obtained  clear  evidence  that  the  fruit  is 
a  three-car peled  pistil.  The  dehisceuce  affords  further  evidence 
of  the  same  thing.  This  dehiscence  is  clearly  septicidal,  for  the 
seeds  are  found  attached  to  the  edges  of  the  valves. 

(2)    Internal  Structure. — Making  a  cross-section   of  the   fruit 


214  LABORATORY    EXERCISES    IN    BOTANY. 

near  its  middle,  preferably  before  it  is  quite  ripe,  and  comparing 
the  structure  with  that  observed  in  the  dehiscing  capsule,  clearest 
evidence  of  its  three-carpeled  character  will  be  found.  The  three 
carpellary  leaves  have  evidently  been  rolled  inward  at  their  mar- 
gins, not  only  until  they  have  met  at  the  centre,  but  until  they 
have  curved  outward  again,  forming  what  is  called  an  axile  pla- 
centation.  In  dehiscence  the  carpels  have  merely  separated  into 
their  original  components. 

(3)  Mode  of  Dispersion. — Here  no  elaborate  means  of  dispersal 
seem  to  be  required.  The  small  brown  seeds  are  not  only  very 
hard,  but  they  are  also  poisonous,  so  that  they  are  not  likely  to 
be  devoured  by  animals.  All  that  is  needed  is  that  the  capsule 
should  open  and  expose  the  seeds  to  the  wind. 

III.  THE  FRUIT  OF  HYOSCYAMUS. — This  fruit  may  be  stud- 
ied  as  the  type  of  that  modification  of  the  capsule  called  the /»//.<•/*. 
The  fruit  is  enclosed  in  the  persistent,  urceolate,  five-toothed,  hairy 
calyx,  which,  however,  is  not  adherent  to  it  and  does  not  properly 
constitute  a  part  of  it. 

(1)  External  Characteristics. — Removing  the  calyx,  it  will  be 
found  that  the  somewhat  urn-shaped  fruit  has  a  length  of  from 
one  to  one  and  one-half  centimetres,  is  usually  somewhat  two- 
lobed  and  rugose,  and  is  dehiscent  by  a  line  that  runs  horizon- 
tally around  it  well  toward  the  top,  so  that  the  upper  portion 
comes  off  like  a  lid.     At  the  apex  of  the  latter  is  seen  the  rem- 
nant of  the  style  in  the  form  of  a  small  rounded  or  conical  prom- 
inence. 

(2)  Internal  Structure. — Removing  the  li'd,  the  fruit  is  found  to 
be  two-celled  and  many-seeded,  the  seeds  being  attached  to  pla- 
centae at  the  axis.     It  is  therefore,  as  one  would  be  led  to  expect 
from  its  two-lobed  exterior,  a  t\Vo-carpeled  fruit.     The  two-celled 
and  two-carpeled  character  are,  however,  not  necessary  to  the  idea 
of  a  pyxis.     The  pyxis  of  some  species  may  be  one-celled,   of 
others  two-,  three-,  or  several-celled.     There  is,  in  other  word>, 
the  same  variety  in  this  respect  among  fruits  of  this   kind   as 
among  ordinary  capsules. 

The  dispersion  in  this  species  is  accomplished  in  a  manner 
analogous  to  that  in  the  Poppy.  After  dehiscence  the  wind,  agi- 
tating the  plant,  will  throw  out  the  seeds,  which,  being  small  and 
light,  will  be  sown  far  and  wide. 


STUDY   OF   SOME   SYNCARPOUS   FRUITS. 


215 


PLATE  XXXII.,  FIG.  1.— Poppy-capsule  (about  natural  size):  a,  stigma;  6,  one  of  the 
valves  of  dehiscence  ;  c,  stalk  of  capsule ;  d,  portion  of  receptacle  on  which  sepals,  petals, 
and  stamens  were  inserted  ;  e,  peduncle. 

FIG.  2.— The  same  in  transverse  section,  showing  marginal  placentation :  a,  one  of  the 
placentae. 

FIG.  3.— Capsule  of  Colchicum  (somewhat  enlarged),  showing  septicidal  dehiscence. 

FIG.  4.— Transverse  section  of  unripe  Fruit,  showing  axile  placentation  and  three- 
carpeled  structure. 

FIG.  5.— Calyx  of  Hyoscyamus,  enclosing  pyxis.    (Somewhat  enlarged.) 

FIG.  6.— Pyxis  of  Hyoscyamus,  showing  its  two-celled  and  two-carpeled  character  and 
its  mode  of  dehiscence. 


EXERCISE  XXVIII. 

FURTHER  STUDY  OF  SYNCARPOUS  FEUITS. 

FROM  the  list  given  at  the  beginning  of  the  last  exercise  are 
selected  the  following  for  this  exercise  :  the  fruit  of  the  Cori- 
ander and  that  of  the  Lemon. 

I.  THE  FRUIT  OF  CORIANDER. — Coriander  belongs  to  the  nat- 
ural order  Umbellifera?,  the  fruits  of  which  have  a  close  family 
resemblance  and  differ  quite  widely  from  those  of  most  other 
plants  in  several  important  particulars.  The  fruits  are  called 
cremocarps,  and  a  cremocarp  may  be  denned  as  an  inferior,  two- 
carpeled  dry  fruit  that  is  usually  ten-ribbed  longitudinally  and  is 
provided  with  oil-tubes  or  vittce,  has  an  epigynous  disk,  and,  when 
ripe,  splits  readily,  usually  spontaneously,  into  two  symmetrical, 
one-seeded  half-fruits  or  mericarps.  .Between  the  primary  ridges 
or  juga  there  sometimes  occur  secondary  or  intermediate  ones. 
The  mericarps  not  infrequently  remain  suspended  for  a  time 
after  dehiscence  from  the  top  of  a  slender  prolongation  of  the 
receptacle,  called  the  carpophore.  This  may  be  either  single  or 
separated  into  two  thread-like  portions  nearly  to  its  base.  The 
oil-tubes,  when  present,  usually  occur  in  the  furrows  between  the 
primary  ribs  or  on  the  commissural  surfaces.  The  two  styles  are 
usually  persistent  and  thickened  at  their  bases  into  bodies  called 
stylopodia.  The  seeds  are  albuminous,  pendulous,  and  anatropotis. 

While  it  is  an  easy  matter  to  distinguish  members  of  this  order 
from  those  of  other  orders  by  their  fruits,  the  latter  also  aiford 
the  best  means  of  distinguishing  the  species  of  the  order  from 
each  other,  since  the  cremocarps  differ  not  only  in  shape  and  size, 
but  also  in  the  number  and  position  of  the  oil-tubes,  in  the  pres- 
ence or  absence  of  secondary  ribs,  in  the  surface  appendages,  etc. 

The  fruits  of  Coriander,  as  in  most  others  of  the  order,  occur 
in  compound  umbels.  The  individual  fruits  are  nearly  spherical 
and  four  or  five  millimetres  long.  At  the  apex  of  each  are  ob- 
served two  stylopodia,  each  rising  to  a  point,  or  sometimes  still 

217 


218  LABORATORY    EXERCISES    IN    BOTANY. 

terminated  by  the  persistent  upper  part  of  the  style  and  stigma. 
Forming  a  circle  about  the  base  of  the  stylopodia  are  five  small 
but  distinct  calyx-teeth.  Careful  scrutiny  will  also  reveal,  inte- 
rior to  these,  the  scars  of  the  deciduous  petals  and  stamens.  The 
fruit  is  therefore  clearly  inferior.  The  ten  primary  ribs  are 
straight  and  distinct,  and  the  ones  at  the  commissure  are  double. 
Between  each  pair  of  primary  ribs  are  more  obscure  secondary 
ones,  which  are  not  straight,  but  wavy  or  zigzag. 

The  fruits  in  this  instance  do  not,  as  a  usual  thing,  sponta- 
neously separate  into  their  mericarps,  but  the  separation  is  easily 
brought  about  by  slight  pressure.  The  commissural  faces  are  then 
seen  to  be  flat  or  slightly  concave,  and  on  the  face  of  each  com- 
missure are  two  oil-tubes,  the  only  ones  this  species  possesses. 

If  a  transverse  section  through  the  middle  of  the  fruit  be  made, 
these  oil-tubes,  whose  contents  are  brown,  may  easily  be  distin- 
guished with  a  magnify  ing-glass.  In  this  section  the  seeds  are 
curved  or  crescentic,  with  the  concave  surfaces  facing  each  other 
in  the  two  mericarps.  A  longitudinal  section  of  the  fruit,  run- 
ning through  the  middle  of  the  two  mericarps,  will  also  show  the 
seed  as  somewhat  curved,  and  the  minute  embryo  may  be  seen 
imbedded  in  the  albumen  at  the  upper  end. 

The  oil-tubes  contain  the  volatile  oil  which  renders  the  fruits 
aromatic,  and  which,  in  this  and  most  other  UmbelliferaB  employed 
in  medicine,  makes  the  fruits  valuable  as  stimulants  and  carmin- 
atives. 

II.  THE  FRUIT  OF  THE  LEMON. — This  may  be  taken  as  typi- 
cal of  the  group  of  fruits  popularly  called  "citrus"  fruits,  but 
termed  botanically  hesperidia. 

(1)  External  Characters. — At  the  base  is  usually  found  the  per- 
sistent five-toothed  calyx,  showing  that  the  fruit  is  superior.  At 
th<-  mammillate'apex  maybe  observed  the  scar  of  the  stylo,  which 
has  withered  and  fallen  away.  The  fruit  is  oblong  or  ellipsoidal 
in  outline,  from  six  to  ten  centimetres  long,  and  rugose  on  tho 
surface.  Imbedded  in  the  outer  portion  of  tho  lio-ht-yollow 
pericarp  are  numerous  rounded  secretion-reservoirs  containing 
the  volatile  oil  which  imparts  the  peculiar  fragrance  to  the  fruit. 
The  fruit  is  fleshy  and  indehisoont,  and  there  are  on  the  surface- 
no  ridges  or  furrows  to  indicate  the  number  of  carpels  of  which 
it  is  composed. 


FURTHER   STUDY    OF   SYNCARPOUS    FRUITS.  219 

(2)  The  Internal  Structure. — Making  a  cross-section  through  the 
middle,  it  will  be  found  that  the  thickish  pericarp  is  differentiated 
into  two  portions — an  outer,  which  is  yellow  and  contains  the 
secretion- vessels  already  mentioned,  and  an  inner  white  and 
spongy  portion  destitute  of  glands. 

Interior  to  the  pericarp  is  the  pulpy  portion,  divided  by  radial 
partitions  into  a  varying  number  of  compartments.  In  the  inner 
angle  of  each  compartment  or  loculus  are  usually  one  or  two 
seeds,  and  these  are  attached  to  the  axis.  The  placentation, 
therefore,  is  axile,  and  there  are  as  many  carpels  in  the  fruit  as 
there  are  loculi,  which  may  be  from  five  to  fifteen  or  more. 

The  pulp  which  contains  the  acid  juice  is  structurally  altogether 
different  from  that  of  the  Cherry,  Peach,  or,  in  fact,  from  that  of 
any  other  fruits  outside  the  family  (AurantiaceaB)  to  which  the 
Lemon  belongs.  The  juice  is  contained  in  numerous  thin-walled 
sacs  which  are  separate  from  each  other  and  are  borne  on  the 
walls  of  the  loculus.  By  tracing  their  development  they  may 
easily  be  proved  to  be  hairs  which  at  first  are  like  ordinary 
simple  plant-hairs,  but  which,  as  the  ovary  develops  into  the 
fruit,  become  thick  and  succulent. 

Citrus  fruits  resemble  berries  except  for  this  peculiarity  of 
their  pulp,  which  justifies  calling  them  by  a  different  name,  that 
of  hesperidia. 

The  seeds  have  a  leathery  testa,  are  anatropous  and  exalbu- 
minous,  and  the  dicotyledonous  embryo  is  frequently  single,  but 
sometimes,  as  in  the  orange,  there  are  two  or  more  embryos  in 
each  seed.  The  cotyledons  are  commonly  somewhat  unequal, 
and  sometimes  there  are  three  or  four  instead  of  two.  The 
plumule  is  usually  well  developed. 

So  far  as  the  relation  of  the  structure  of  this  fruit  to  the  dis- 
persion of  the  plant  is  concerned,  it  may  be  remarked  that  the 
volatile  oil  in  the  pericarp  is  probably  defensive  against  the 
attacks  of  insects  and  fungi,  while  not  preventing  the  fruits 
from  being  eaten,  when  ripe,  by  larger  animals.  The  seeds, 
while  not  specially  protected  by  a  hard  enclosure,  are  neverthe- 
less probably  rejected,  as  a  usual  thing,  by  animals  that  feed  upon 
the  fruits,  by  reason  of  their  bitter  taste. 


FURTHER   STUDY   OF   SYNCARPOUS   FRUITS. 


221 


a 


PLATE  XXXIII.,  FIG.  1.— Fruit  of  Coriander  (enlarged  about  6  times) :  a,  one  of  the 
stigmas  sometimes  persisting  until  the  fruit  is  ripe ;  b,  one  of  the  stylopodia;  c,  one  of 
the  calyx-teeth ;  d,  one  of  the  primary  ribs ;  e,  one  of  the  secondary  ribs. 

FIG.  2.— Transverse  section  through  one  of  the  Cremocarps  (enlarged  about  8  diam- 
eters) :  a,  one  of  the  primary  ribs ;  b,  seed ;  c,  one  of  the  villse  or  oil-tubes ;  d,  one  of  the 
secondary  ribs. 

FIG.  3.- Lemon  (%  natural  size) :  a,  nipple-shaped  apex ;  6,  calyx  at  base. 

FIG.  4— Transverse  section  of  the  same,  showing  placenlation :  a,  glandular  portion 
of  pericarp ;  b,  a  seed  ;  c,  one  of  the  pulp-sacs,  modified  hairs. 


EXERCISE  XXIX. 

STUDY  OF  ACCESSORY   FKUITS. 

THE  following  are  convenient  for  study  :  the  Strawberry  (Fra- 
garia  Virgiuiana,  Mill.,  or  F.  vesca,  £.),  the  Rose  (the  hips  of  any 
one  of  our  common  species,  as  Rosa  setigera,  Miehx.,  R.  Carolina, 
L.,  or  R.  rubiginosa,  L.\  the  Mulberry  (Morus  rubra,  L.\  the 
Wintergreen  (Gaultheria  procumbens,  L.),  the  Pineapple  (Ana- 
nassa  sativa,  Lind.),  and  the  Fig  (Ficus  Carica,  L.). 

From  this  list  are  selected  for  the  present  study  the  fruits  of 
the  Wintergreen  and  the  Fig. 

I.  THE  WINTERGREEN  is  an  ericaceous  plant  very  common  in 
most  portions  of  the  Eastern  United  States,  and  it  is  particularly 
abundant  in  those  portions  of  the  country  which  abound  in  pines 
or  other  needle-leaved  evergreens.  From  the  thin,  trailing  stem 
or  rhizome  rise  vertically,  to  the  height  of  from  three  to  six 
inches,  slender,  usually  simple  branches  which  bear  a  few  crowded 
alternate  or  apparently  whorled  evergreen  leaves. 

The  plant  bears  its  white,  nodding,  urceolate  blossoms  singly  in 
the  axils  of  the  leaves.  The  blossoming  is  in  June  and  July,  and 
the  scarlet,  berry-like  fruits  are  matured  in  late  summer  or  in 
early  autumn,  but  persist  on  the  plant  until  late  in  the  succeed- 
ing spring. 

(1)  External  Characteristics. — The  so-called  berries  are  nearly 
spherical,  about  a  centimetre  in  diameter,  somewhat  depressed  and 
bracteolate  at  the  base,  with  five  fleshy  teeth  at  the  apex,  and  with 
a  simple  persistent  style. 

The  five  teeth  referred  to  are  really  the  limb  of  the  persistent 
gamosepalous  calyx,  which  in  fruit  develops  considerably,  be- 
comes succulent,  acquires  a  scarlet  color,  and  constitutes  the 
really  edible  part  of  the  fruit.  This  is  clearly  evidenced  by  a 
study  of  the 

(2)  Internal  Structure. — On  making  a  transverse  section  well 
toward  the  apex  of  the  fruit  there  will  be  observed  a  five-celled, 

223 


224  LABORATORY    EXERCISES    IN    BOTANY. 

many-seeded,  dry  or  non-succulent  body,  the  real  fruit,  surrounded 
by  a  circle  of  five  fleshy  pieces  having  an  imbricate  arrangement 
— the  calyx-teeth  before  referred  to.  Such  a  section  is  shown  on 
Plate  XXXIV.  (Fig.  4),  but  the  fact  is  even  more  distinctly  seen 
by  examining  a  longitudinal  section,  as  shown  on  Plate  XXXIV. 
(Fig.  2) ;  if  any  further  doubt  still  existed,  it  could  easily  be  dis- 
pelled by  tracing  the  development  of  the  fruit  from  the  flower. 

The  fruit  is,  then,  in  reality  an  indehiscent  capsule  with  a  fleshy 
accessory  calyx,  and  is  not  a  berry  at  all,  for  a  berry  is  an  inde- 
hiscent fruit  with  a  wholly  succulent  pericarp — as,  for  example, 
the  cranberry,  gooseberry,  and  grape.  The  fruit  bears  more  re- 
semblance to  a  pome  such  as  the  apple,  but  differs  from  it  in  the 
fact  that  the  calyx  is  not  adnate  to  the  fruit  proper,  and  the  latter 
is  dry,  not  succulent. 

(3)  Dispersion. — Undoubtedly,  in  this  as  in  most  other  showy 
fruits  the  bright  color  and  the  agreeable  taste  cause  the  fruit  to  be 
eaten  by  animals.  The  seeds,  on  account  of  their  minuteness,  are 
not  likely  to  escape  when  the  fruit  is  eaten,  but,  being  hard  and 
probably  much  less  digestible  than  the  rest,  many  of  them  are 
likely  to  survive  the  action  of  the  gastric  juice,  and  to  emerge 
from  the  alimentary  canal  of  the  animal  in  a  condition  fit  for 
germination. 

II.  THE  FIG. — This  fruit,  easily  obtained  in  the  dried  form 
in  our  markets  at  all  seasons  of  the  year,  is  best  studied  by  soak- 
ing specimens  in  water  to  which  a  little  ammonia  has  been  added, 
to  swell  them  to  their  original  dimensions. 

(1)  External  Characteristics. — The  fruit  is  pyriform  in  shape, 
smooth   or  somewhat  longitudinally   striate  on   the  outside,  de- 
pressed and  with  a  small  aperture  at  the  apex  which  opens  into 
the  hollow  interior,  and  at  the  base  tapering  into  a  woody  stem. 
The  rest  of  the  fruit  is  soft  and  pulpy — in  fact,  so  far  as  mere 
external  appearances  go,  it  might  easily  be  mistaken  for  a  fruit 
essentially  like  a  pear.     A  careful  study  of  its  internal  structure 
and  its  mode  of  development,  however,  shows  that  the  fig  is  alto- 
gether different. 

(2)  Internal  Structure. — A  longitudinal  section  through  the  cen- 
tre shows  that  the  small  aperture  at  the  apex  communicates  with 
a  considerable  cavity  in  the  interior,  and  the  walls  of  this  are- 
lined  with  numerous  small  seed-like  bodies.     These,  however,  on 


STUDY    OF    ACCESSORY    FRUITS.  225 

close  inspection  are  found  not  to  be  seeds,  but  small  fruits  (utri- 
cles), each  with  a  single  seed  loosely  enclosed  in  a  thin,  dry 
pericarp.  Each  fruitlet,  as  may  easily  be  seen  by  studying  its 
development,  is  the  product  of  a  single  small  flower. 

In  examining  the  Fig  in  blossom  it  would  be  difficult  for  the 
novice  even  to  find  the  flowers,  as  he  would  scarcely  think  of  look- 
ing for  them  concealed  in  the  ends  of  twigs.  These  twigs,  more- 
over, do  not  look  very  different  from  the  ordinary  ones,  except 
that  they  are  slightly  thickened  and  pyriform  at  the  apex,  and 
bear  just  below  this  thickened  portion  a  few  scaly  bracts  instead 
of  true  leaves.  The  minute  aperture  at  the  apex,  closed  as  it  is 
by  scales,  might  easily  escape  observation  altogether. 

If  a  longitudinal  section  of  one  of  these  branches  be  made, 
there  will  be  found  in  the  interior  hollow  a  few  minute  staminate 
flowers  located  near  the  apical  aperture,  and  .very  numerous  small 
pistillate  flowers  occupying  the  remainder  of  the  interior  sur- 
face. The  former  consist  of  a  gamosepalous,  three-parted  calyx 
and  three  introrse  stamens ;  the  latter  also  consist  of  a  gamo- 
sepalous calyx  (which,  however,  may  be  from  three-  to  five- 
parted)  and  a  single  one-ovuled  pistil  which  has  a  style,  inserted 
more  or  less  laterally,  and  a  two-lobed  stigma.  The  flowers  are 
also  stalked,  and  in  development  the  stalks  and  calyx  become 
fleshy,  while  the  fruit  proper  becomes  dry  and  utricle-like  or 
achenium-like. 

It  will  thus  be  seen  that  what  is  called  the  fig  is  not  a  single 
fruit,  but  a  multiple  or  collective  one ;  but  it  is  also  something 
more,  for  the  greater  portion  of  its  bulk  is  composed  of  the  suc- 
culent hollow  receptacle.  Such  a  multiple  fruit  with  an  accessory 
receptacle  has  been  called  by  botanists  a  syconium. 

(3)  Mode  of  Dispersion. — Regarding  this  it  may  be  remarked 
as  significant  that,  besides  being  attractive  and  palatable  when 
ripe,  the  seeds  possess  laxative  properties  which  doubtless  render 
them  more  likely  to  escape  digestion,  and  at  the  same  time  ensure 
their  dispersion  by  frugivorous  birds  and  mammals. 

15 


STUDY   OF    ACCESSORY    FRUITS. 


227 


PLATE  XXXIV.,  FIG.  1.— Whole  Plant  of  Wintergreen  in  fruit  (%  natural  size). 

FIG.  2.— Longitudinal  section  of  one  of  the  Fruits  (enlarged) :  a,  bract  at  the  base  ;  b, 
fleshy  calyx  ;  c,  fruit  proper;  d,  persistent  style. 

FIG.  3.— View  of  upper  end  of  Fruit,  showing  the  five  calyx-teeth,  the  upper  end  of 
the  capsule,  and  the  style. 

FIG.  4.— View  of  cross-section  through  the  upper  part  of  one  of  the  Fruits,  showing 
the  five-celled,  many-seeded  capsule  surrounded  by  the  calyx. 

FIG.  5.— Longitudinal  section  of  a  Fig  (about  natural  size) :  a,  apical  aperture ;  6,  one 
of  the  fruitlets  ;  c,  hollow  receptacle ;  d,  one  of  the  bracts  at  the  base. 


FORM   FOR  THE  STUDY   OF  FRUITS. 


I.  SIZE. 

(6)  Farinaceous     interi- 

Loment. 

»    1.  Length. 
2.  Breadth. 

orly. 
(7)  Oily  throughout. 

Cochlea. 
Capsule. 

3.  Thickness. 

(8)  Oily  exteriorly. 
(9)  Oily  interiorly. 

Septicidal      de- 
hiscence. 

II.  COLOR. 

(10)  Waxy  exteriorly. 
(11)  Coriaceous   through- 

Septifragal   de- 
hiscence. 

1.  Exteriorly. 

out. 

Loculicidal  de- 

2.  Interiorly. 

(12)  Coriaceous  exteriorly 

hiscence. 

(13)  Coriaceous  interiorly 

Porous      dehis- 

III.  SHAPE. 
1.  Globose. 
2.  Depressed-globular. 
3.  Oblong. 
4.  Ovoid. 

(14)  Ligneous  throughout 
(15)  Ligneous  exteriorly. 
(16)  Ligneous  interiorly. 
(17)  Fibrous  exteriorly. 
(18)  Corneousthroughout. 
(19)  Corneous  exteriorly. 

cence. 
Silique. 
Silicle. 
Pyxis. 
(2)  More  than  one  pistil, 
a.  Etaerio. 

5.  Conical. 
6.  Pyriform. 
7.  Flattened. 
8.  Winged. 
9.  Ribbed. 

Ifl      T  r^Horl 

(20)  Corneous  interiorly. 
(21)  Bony  throughout. 
(22)  Bony  exteriorly. 
(23)  Bony  interiorly. 
2.  Number  of  loculi. 

6.  Strawberry, 
c.  Hip    or    cynarrho- 
dium. 
6.  Product  of  floiver-duster. 
(1)  Sorosis. 

1U.    -LiODCQ. 

11.  Nodular. 
12.  Irregular. 

(1)  Unilocular. 
(2)  Bilocular. 
(3)  Trilocular. 

(2)  Syconium. 
(3)  Strobile. 
(4)  Galbulus. 

(4)  Quadrilocular. 

IV.  SURFACE  AND   APPEND- 

AGKS 

(5)  Quinquelocular. 
(6)  Sexilocular. 

VII.  TASTE. 

1.  Glabrous. 

(7)  Multilocular. 
3.  Seeds  in  each  loculus. 

1.  Insipid. 
2.  Bland. 

2.  Polished. 

(1)  One. 

3.  Sweet. 

3.  Glaucous. 

(2)  Two. 

4.  Bitter. 

4.  Punctate. 

(3)  Several. 

5.  Mucilaginous. 

5.  Glandular-hairy. 
6.  Rugose. 

+     (4)  Many. 

6.  Pungent. 
7.  Acrid. 

7.  Scabrous. 

8.  Warm. 

8.  Verrucose. 

VI.  KIND. 

9.  Burning. 

9.  Pubescent. 

1.  Inferior. 

10.  Cooling. 

10.  Puberulent. 

2.  Superior. 

11.  Astringent. 

11.  Sericeous. 
12.  Lanugiuous. 

3.  With  accessory  organs. 
(1)  Accessory  calyx. 

12.  Nauseous. 
13.  Prickling. 

13.  Tomentose. 

(2)  Accessory  involucre. 

14.  Saline. 

14.  Villose. 

(3)  Accessory  receptacle. 

15.  Alkaline. 

15.  Pilose. 

4.   Without  accessory  organs. 

16.  Acidulous. 

16.  Floccose. 

5.  Product  of  single  flower. 

17.  Hispid. 
18.  Strigose. 

.     (1)  Of  one  pistil, 
a.  Indehiscent. 

VIII.  ODOR. 

19.  Spinose. 

Akene. 

1.  Odorless. 

20.  Echinate. 

Utricle. 

2.  Faint. 

21.  Aculeate. 

Caryopsis. 

3.  Agreeable. 

22.  Pappiferous. 

Samara. 

4.  Aromatic. 

Double  samara. 

5.  Mint-like. 

V..  INTERNAL  STRUCTURE. 

Glans. 
Cremocarp. 

6.  Balsamic. 
7.  Camphoraceous. 

1.  Texture  of  pericarp. 
(1)  Succulent     through- 

Drupe. 
Tryma. 

8.  Terebinthinous. 
9.  Pungent. 

out. 

Berry. 

10.  Musky. 

(2)  Succulent  exteriorly. 

Hesperidium. 

11.  Disagreeable. 

(3)  Succulent  interiorly. 

Pepo. 

12.  Irritating. 

(4)  Farinaceous  through- 

Pome. 

13.  Nauseous. 

out. 

6.  Dehiscent  forms. 

14.  Narcotic. 

(5)  Farinaceous     exteri- 

Follicle. 

15.  Putrid. 

orly. 

Legume. 

16.  Fetid, 

EXERCISE  XXX. 

STUDY   OF   EXALBUMINOUS  SEEDS. 

THE  following  plants  afford  good  examples  for  study  :  the 
Pumpkin  (Cucurbita  Pepo,  L.),  the  Watermelon  (Cucurbita  ci- 
trullus,  Schrader),  the  Pea  (Pisum  sativum,  L.\  the  Scarlet  Run- 
ner (Phaseolus  multiflorus,  Willd.\  the  Silver  Maple  (Acer  dasy- 
carpum,  Ehrh.\  the  White  Oak  (Quercus  alba,  L.),  the  Overcup 
Oak  (Quercus  macrocarpa,  Michx.),  the  Apple  (Pyrus  Mains,  L.), 
the  Orange  (Citrus  aurantium,  £.),  the  Peach  (Amygdalus  Per- 
sica,  L.),  the  Plum  (Prunus  domestica,  L.\  the  Almond  (Prunus 
Amygdalus,  Stokes),  and  the  Walnut  (Juglans  nigra,  L.). 

From  this  list  are  selected  for  this  exercise  the  seeds  %of  the 
Almond  and  the  Pumpkin. 

First  will  be  considered  the  seed  in  general.  It  may  be  defined 
as  the  ripened  ovule.  It  is  the  end  for  which  the  flower  and  fruit 
exist,  the  finished  product  of  the  reproductive  process  in  flower- 
ing plants.  Being  a  ripened  ovule,  it  usually  bears  some  general 
resemblance  to  the  organ  from  which  it  was  developed.  Like  the 
ovule,  it  may  be  atropous,  anatropous,  amphitropous,  or  campylot- 
ropous ;  it  usually  possesses  two  coats,  corresponding  respectively 
to  the  primine  and  secundine  of  the  ovule,  though  often  quite  dif- 
ferent from  these  in  their  texture,  and  called  by  different  names,  to 
wit,  the  testa  and  the  tegmen;  the  micropyle  is  usually  still  recog- 
nizable as  a  scar  at  the  apex  of  the  seed  ;  the  chalaza  often  has  its 
position  marked  by  a  spot  or  scar  more  or  less  distinctly  recogniz- 
able, and  the  raphe',  if  present  in  the  ovule,  is  frequently  still  trace- 
able as  a  line  or  a  ridge  on  one  side  of  the  seed.  Of  course,  as  a  usual 
thing,  great  changes  have  taken  place  in  the  size,  shape,  and  text- 
ure, and  exceedingly  important  ones  in  the  structure,  of  the  nucellus, 
for  within  it  an  embryo  more  or  less  conspicuous  has  been  formed, 
and  in  many  instances  extra  food  materials  have  been  laid  up  in  the 
form  of  either  endosperm  or  perisperm  or  both. 

As  a  matter  of  great  practical  importance  in  the  study  of  seeds, 

229 


230  LABORATORY    EXERCISES    IN    BOTANY. 

it  should  be  noted  that  every  seed  possesses  at  least  two,  and  usu- 
ally only  two,  scars,  that  of  the  micropyle  and  that  called  the 
hilum,  the  latter  marking  the  place  where  the  seed  has  broken 
away  from  its  funiculus  or  from  the  placenta.  One  may  tell  by 
the  relative  position  of  these  scars  whether  the  seed  is  atropous, 
anatropous,  campylotropous,  or  amphitropous — always  an  im- 
portant point  to  determine.  If  the  seed  is  straight  and  the  two 
scars  are  at  opposite  ends,  the  seed  is  atropous;  if  it  is  straight 
and  the  two  scars  are  adjacent  to  each  other  at  one  end,  it  is  anat- 
ropous;  if  straight  and  the  chalaza  is  at  one  end,  the  micropyle 
at  the  opposite  one,  and  the  hilum  intermediate  between  the  two, 
it  is  amphitropous ;  and  if  the  seed  is  bent  or  curved  so  that  the 
opposite  ends  and  the  two  scars  are  approximated,  it  is  campylot- 
ropous. 

In  some  seeds  the  nucellus  consists  wholly  of  embryo ;  that  is, 
the  seeds  possess  no  extra  food  store,  and  are  hence  called  exalbumi- 
nouSj  a.s  was  found  to  be  the  case  with  the  Cherry ;  other  seeds  possess 
both  the  embryo  and  the  extra  food  store :  they  are  described  as 
albuminous.  In  an  albuminous  seed  the  albumen  or  extra  food 
store  may  be  developed  either  wholly  within  the  embryo-sac  or 
outside  of  it.  In  the  former  case  the  albumen  is  called  endosperm  ; 
in  the  latter,  perisperm.  In  a  few  seeds  both  endosperm  and  peri- 
sperm  are  present. 

I.  THE  ALMOND  SEED. — The  fruit  of  the  Almond  is  drupa- 
ceous like  the  peach  and  the  cherry,  only  the  sarcocarp  is  less 
succulent  and  is  not  employed  for  food.  The  almond  of  the 
markets  corresponds  to  the  pit  of  the  peach ;  that  is,  the  outer 
hard  part  is  endocarp  and  contains  the  seed. 

(1)  External  Characteristics. — Carefully  removing  the  seed,  so 
as  to  observe  its  attachments,  it  will  be  noticed  that  it  has  on  one 
edge,  near  its  smaller  end,  a  narrow  hilum-scar  extending  up  along 
the  edge  of  the  seed  from  one-third  to  one-half  of  the  length  of 
the  latter.  At  the  small  end  of  the  seed,  immediately  adjoining 
one  end  of  this  scar,  is  the  small  but  distinct  micropyle-scar. 
These  scars  being  adjacent  and  the  body  of  the  seed  not  being 
bent,  the  seed  is  known  to  be  anatropous.  At  or  near  the  largo 
end  may  be  seen  a  roundish  spot,  often  darker  than  the  rest  of 
the  surface,  where  the  two  coats  still  adhere  to  each  other :  this  is 
the  chalaza.  From  this  point  veins  are  seen  to  radiate  and  con- 


STUDY   OF    EX  ALBUMINOUS   SEEDS.  231 

verge  toward  the  opposite  end.  On  the  hilum  edge  may  also  be 
traced  a  straight  line  and  a  slight  ridge  which  connects  the  hilum 
and  chalaza  :  this  is  the  raphe. 

The  general  outline  of  the  seed  is  ovate ;  it  is  flattish,  some- 
what wrinkled  from  drying,  and  more  or  less  longitudinally 
striate.  The  length  is  from  two  to  two  and  one-half  centi- 
metres, the  width  from  one  to  one  and  one-half  centimetres,  and 
the  greatest  thickness  from  one-half  to  three-fourths  of  a  centi- 
metre. The  testa  is  thin  and  brown ;  it  is  also  scurfy  from  large, 
bladdery,  exterior  cells. 

(2)  Internal  Structure. — Soaking  the  seed  in  water  for  a  few 
hours  and  removing  the  coats,  the  latter  are  found  to  be  two  in 
number  and  quite  distinct  except  at  the  chalaza ;  the  inner  one 
is  membranous  and  white,  and  covers  the  white  nucellus.     The 
latter  is  found  to  consist  wholly  of  embryo;  the  seed,  therefore, 
is  exalbuminous. 

The  embryo  is  straight ;  that  is,  the  radicle  and  the  cotyledons 
point  in  opposite  directions.  The  cotyledons  are  large  and  thick, 
constituting  much  the  larger  part  of  the  whole  embryo.  As  shown 
in  the  illustration  (PI.  XXXV.,  Fig.  2),  they  are  not  always 
equal,  but  one  may  be  considerably  larger  than  the  other.  They 
are  usually  more  or  less  cordate  at  the  base.  The  radicle  and 
caulicle,  though  relatively  small,  are  distinctly  recognizable  by 
the  naked  eye,  as  is  also  the  plumule,  which  is  well  developed. 

(3)  Tests. — Applying  iodine  solution  to  a  freshly-cut  surface, 
it  will  be  observed  that  no  blue  color  is  developed,  and  therefore 
no  starch  is  present.     If  the  solution  be  strong,  however,  a  brown 
color  is  produced,  which  indicates  the  presence  of  proteids.     But 
the  great  bulk  of  the  food  material  stored  in  the  embryo  consists 
of  fixed  oil.     The  presence  of  the  latter  may  be  proved  by  thor- 
oughly warming  the  freshly-cut  surface  of  a  seed  and  rubbing  it 
on  a  clean  sheet  of  white  paper,  when  a  non-volatilizable  greasy 
spot  will  be  left. 

II.  THE  PUMPKIN  SEED. — -(1)  External  Characteristics. — The 
seeds  are  smooth,  white,  oblong-ovate,  strongly  flattened,  with  a 
raised  border  extending  from  the  smaller  end  around  the  edge  to 
the  same  end.  The  hilum  and  micropyle-scars  are  located  side  by 
side  at  the  smaller  end  of  the  seed,  and,  though  not  large,  are 
distinct.  The  chalaza  is  at  the  opposite  end,  but  the  raphe'  in  the 


232  LABORATORY    EXERCISES    IN    BOTANY. 

fully-developed  seed  merges  into  the  border  above  described,  and 
is  no  longer  recognizable.  The  length  of  the  seed  is  about  two 
centimetres,  its  greatest  breadth  about  one  centimetre,  and  its 
greatest  thickness  about  two  millimetres. 

(2)  Internal  Structure. — The  testa  is  coriaceous  in  texture  and 
distinct  from  the  thin,  membranous,  olive-green  tegmeu,  which 
immediately  envelops  the  embryo,  there  being  no  albumen. 

The  embryo  consists  of  two  oblong-ovate  or  elliptic,  equal 
cotyledons,  flat  on  their  applied  faces  and  convex  on  their  exte- 
rior ones,  each  provided  with  about  seven  veins  radiating  from 
the  base  to  the  entire  margin. 

The  caulicle  and  radicle  together  form  a  small,  somewhat  flat- 
tened cone,  and  the  plumule  exists  only  as  the  merest  conical 
point  between  the  bases  of  the  cotyledons.  It  is,  in  fact,  but  an 
epicotyl,  and  not  a  plumule  in  the  proper  sense,  no  leaves  being 
developed  upon  it  until  after  germination  begins. 

Tests  show  that  the  seed  possesses  abundance  of  albuminous  and 
oily  matter,  but  no  starch. 


STUDY   OF   EXALBUMINOUS   SEEDS. 


233 


PLATE  XXXV.,  FIG.  1.— Almond  Seed  (about  natural  size) :  a,  chalaza ;  b,  raphe" ;  c, 
hilum ;  d,  micropyle. 

FIG.  2.— The  same  with  the  seed-coats  removed,  consisting  wholly  of  embryo :  a,  the 
larger  of  the  two  cotyledons  partly  concealed  behind  the  smaller  one,  6;  c,  the  radicle. 

FIG.  3.— The  same  cut  lengthwise  through  the  middle  of  the  two  cotyledons  and  the 
radicle  :  a,  larger  cotyledon ;  6,  smaller  cotyledon ;  c,  plumule ;  d,  caulicle  ;  e,  one  of  the 
projecting  lower  lobes  of  the  larger  cotyledon. 

FIG.  4.— Seed  of  Pumpkin  (about  natural  size) :  a,  chalaza ;  6,  raised  border ;  c,  hilum  ; 
d,  micropyle. 

FIG.  5.— Embryo  of  same,  showing  outer  face  of  one  of  the  cotyledons,  a,  the  caulicle, 
b,  and  the  radicle,  c. 

FIG.  6.— Embryo  of  same,  cut  vertically  through  the  middle  of  the  cotyledons :  a,  one 
of  the  cotyledons ;  6,  the  epicotyl,  scarcely  yet  developed  into  a  plumule ;  c,  the  radicle. 


EXERCISE  XXXI. 
STUDY  OF  ALBUMINOUS  SEEDS. 

SEEDS  of  the  following  plants  are  not  difficult  to  obtain  and 
are  good  for  study:  the  Common  Morning-glory  (Ipomsea  pur- 
purea,  Lam.\  Stavesacre  (Delphinium  Staphisagria,  L.\  the  Yel- 
low Pond-lily  (Nuphar  advena,  Ait.\  Sweet  Cicely  (Osmorrhiza 
longistylis,  -DC.),  Nux  Voraica  (Strychnos  Nux-vomica,  L.),  Da- 
tura Stramonium,  L.),  Castor  Bean  (Ricinus  communis,  £.),  Cro- 
ton-oil  Plant  (Croton  Tiglium,  L.\  Yellow  Dock  (Rumex  crispus, 
L.)9  and  Black  Pepper  (Piper  nigrum,  L.). 

For  this  exercise  the  Castor  Bean  and  Black  Pepper  are  selected. 

I.  THE  CASTOR  BEAN. — These  seeds  are  easily  obtainable  from 
druggists  or  from  dealers  in  agricultural  seeds. 

(1)  External  Characteristics. — They  are  ovate  or  elliptical  in 
outline,  convex  on  one  side  and  on  the  other  flattish,  or  rather 
with  two  flattish  surfaces  inclined  at  a  very  obtuse  angle  to  each 
other.      The  two  surfaces  are  shown  respectively  in  Figures  1 
and  2  (PI.  XXXVI.).     The  seeds  measure  from  one  to  one  and 
one-half  centimetres  in  length,  from  six  to  nine  millimetres  in 
width,  and  from  four  to  six  millimetres  in  thickness.    At  one  end 
is  a  rounded  or  more  or  less  two-lobed  strophiole  or  caruncle  which 
partly  conceals  the  hilum  and  micropyle,  located  side  by  side  at 
the  same  end.     The  chalaza  is  usually  evident  to  the  eye  as  a 
somewhat  elevated  point  near  the  opposite  end.     Between  the 
hilum  and  the  chalaza,  on  the  flatter  side  of  the  seed,  may  be 
traced  the  straight  raphe,  which  appears  as  a*slight  ridge. 

The  whole  surface,  except  the  brownish  or  yellowish  strophiole, 
is  maculate  with  irregular  reddish-brown  spots  and  lines  on  a 
light-brown  or  grayish  background.  The  surface  is  also  smooth 
and  polished. 

(2)  Internal  Structure. — It  is  usually  best,  as  a  preliminary  to 
the  dissection  of  a  seed,  to  soak  it  for  a  few  hours  in  water,  but 
in  this  instance  it  is  hardly  necessary.     Removing  the  outer  coat 

235 


236  LABORATORY    EXERCISES    IN    BOTANY. 

or  testa,  it  is  found  to  be  thickish,  hard,  brittle,  and  of  a  chocolate- 
brown  color  in  the  interior.  The  tegrnen  is  thin,  membranous, 
and  silvery-white. 

The  nucellus  consists  of  a  white,  oily  albumen  enclosing  a  well- 
developed,  straight  embryo.  Its  structure  is  best  demonstrated 
by  first  placing  the  edge  of  the  knife  at  one  end,  in  a  direction 
parallel  to  its  longer  transverse  diameter,  and  exerting  gentle 
pressure  upon  it.  This  will  usually  cause  the  nucellus  to  split 
between  the  cotyledons  with  very  little  injury  to  the  parts,  and 
showing  well  their  structure  and  relations.  Plate  XXXVI. 
(Fig.  3)  shows  the  parts  thus  exposed. 

The  embryo  consists  of  two  elliptical,  entire-margined,  thin, 
cordate  cotyledons,  each  with  three  ribs  radiating  from  its  base 
and  branching  to  form  a  network.  The  caulicle  and  radicle 
together  form  a  small  terete  or  somewhat  fusiform  body,  the 
radicular  end  of  which  lies  close  to  the  exterior  surface  of  the 
albumen,  adjacent  to  the  micropyle. 

The  albumen  possesses  no  starch,  but  abundance  of  fixed  oil 
and  numerous  large  aleurone-grains  containing  crystalloids  and 
globoids.  These,  however,  cannot  be  seen  without  the  aid  of  a 
compound  microscope. 

One  can  hardly  fail  to  notice  that  when  the  seeds  lie  upon  the 
ground,  convex  side  up,  they  bear  a  close  resemblance  to  some 
beetles.  It  has  been  suggested  that  this  mimicry  may  be  of  ad- 
vantage to  the  species  in  aiding  the  dispersion  of  the  seeds,  birds 
picking  them  up  and  swallowing  them  by  mistake  for  insects.  In 
this  case  the  cathartic  properties  of  the  seeds  would  probably  pre- 
vent digestion,  and  they  would  be  dropped  in  fit  condition  for 
germination. 

II.  THE  BLACK-PEPPER  SEED. — Black  Pepper,  as  we  obtain 
it  in  the  market,  is  the  dried  unripe  fruit  of  the  plant,  and  the 
fruit,  often  called  a  berry,  is  really  a  one-seeded  drupe.  The  black, 
wrinkled,  outside  portion  is  the  shrunken  sarcocarp  enclosing  a 
rather  thin  but  hard  putamen,  which  in  turn  encloses  the  seed. 
But,  owing  to  the  time  of  gathering,  the  seed  of  the  Black  Pep- 
per is  seldom  in  a  condition  fit  for  study.  White  Pepper  is  more 
favorable  for  this  purpose,  for  this  is  only  the  fruit  of  the  same 
species  of  plant  which  has  been  permitted  to  become  ripe,  or 
nearly  so,  and  which  has  been  deprived  of  its  sarcocarp.  The 


STUDY    OF    ALBUMINOUS   SEEDS.  237 

grains  should  be  soaked  for  several  hours  in  water,  and  then 
longitudinal  sections  should  be  made  of  them. 

Internal  Structure. — Interior  to  the  thin  seed-coats,  which  lie 
in  close  contact  with  the  wall  of  the  endocarp,  is  a  large  quan- 
tity of  albumen  and  a  relatively  minute  embryo.  The  seed  is 
erect  and  orthotropous,  and  the  embryo  is  straight,  with  its  radicle 
close  to  the  micropyle..  But  a  point  worthy  of  special  note  is  the 
fact  that  the  albumen  is  not  all  alike  :  it  is  divided  into  two  dis- 
tinct portions,  separated  from  each  other  by  a  sharp  line  and  dif- 
fering from  each  other  in  texture  and  color.  One  of  them  is 
light-colored,  even  white,  and  occupies  a  small  area  at  the  apex 
of  the  seed  ;  it  is  the  part  in  which  the  embryo  is  imbedded.  The 
other  is  darker,  harder,  freely  besprinkled  with  secretion-cells, 
and  occupies  all  the  rest  of  the  interior  of  the  seed.  These  two 
portions  of  the  albumen,  though  serving  the  same  purpose,  are 
really  quite  different  in  their  origin  :  the  former  is  the  endosperm, 
so  called  because  it  is  developed  within  the  embryo-sac  of  the  ovule 
while  the  embryo  is  developing ;  the  latter  is  the  perisperm  :  it  is 
equally  a  food  store,  but  is  developed  outside  the  embryo-sac  in  the 
nucellus. 

In  the  great  majority  of  seeds  that  possess  an  albumen  the  latter 
consists  of  endosperm  only,  the  embryo-sac  absorbing  all  the  rest 
of  the  nucellus  into  itself  in  the  process  of  its  development ;  in  a 
few  instances,  as  in  Pepper,  both  the  embryo-sac  with  its  contents 
and  that  portion  of  the  nucellus  exterior  to  the  embryo-sac  de- 
velop pari  passu,  and  both  endosperm  and  perisperm  are  found  in 
the  mature  seed ;  and  in  a  few  other  cases  the  albumen  consists  of 
perisperm  only,  the  endosperm  at  first  developed  being  absorbed 
by  the  embryo  before  the  seed  matures.  This  is  the  case  with  the 
Canna  of  our  gardens. 


STUDY   OF   ALBUMINOUS   SEEDS. 


239 


PLATE  XXXVI.,  FIG.  1.— Castor  Bean  (about  natural  size) :  view  of  convex  surface. 
FIG.  2.— The  same :  view  of  fatter  of  the  two  sides :  a,  strophiole ;  6,  raph6  ;  c,  chalaza. 

FIG.  3.— Nucellus  of  Castor  Bean,  laid  open  so  as  to  show  embryo  :  a,  albumen;  b,  one 
of  the  cotyledons;  c,  caulicle. 

FIG.  4.— Nucellus  of  Castor  Bean,  cut  vertically  in  such  a  manner  that  the  section  passes 
through  the  middle  of  both  cotyledons:  a,  albumen;  b,  one  of  the  cotyledons;  c,  cau- 
licle. 

FIG.  5.— Drupe  of  Black  Pepper  (magnified  about  3  diameters). 

FIG.  6. — The  same  in  longitudinal  section  :  a,  apex  of  fruit,  showing  scar  of  style;  6, 
embryo ;  c,  endosperm  ;  d,  sarcocarp  containing  oil-cells ;  e,  putameu  or  endocarp ;  /, 
seed-coats;  g,  perisperm. 


EXERCISE  XXXII. 

STUDY  OF  SEEDS :  MONOCOTYL  AND  DICOTYL  EMBRYOS. 

AMONG  seeds  having  monocotyledonous  embryos  the  following 
are  suitable  for  study  :  the  Indian  Corn  (Zea  Mays,  L.\  the  Wheat 
(Triticum  vulgare,  Villars),  the  Oat  (A vena  sativa,  L.},  the  Bar- 
ley (Hordeum  distichon,  L.\  the  Canua  (Canna  edulis,  Ker\  the 
Date  Palm  (Phoenix  dactylifera,  L.\  the  Cocoanut  Palm  (Cocos 
nucifera,  L.),  and  the  Water  Plantain  (Alisma  Plantago,  L.). 

Among  those  with  polycotyledonous  embryos  almost  any  spe- 
cies of  the  genus  Pinus  may  be  selected,  but  especially  those  with 
large  seeds,  such  as  Pinus  mouophylla,  Torr.,  Pinus  flexilis,  James, 
Pinus  Torreyaua,  Parry,  and  Pinus  pouderosa,  Douglass. 

I.  A  SEED  HAVING  A  MONOCOTYLEDONOUS  EMBRYO. — A  se- 
lection is  made  of  the  seed  of  the  Indian  Corn.  What  is  commonly 
called  the  seed,  however,  is  really  a  one-seeded  fruit  whose  peri- 
carp-wall is  thin  and  closely  adherent  to  the  coats  of  the  seed. 
Such  a  fruit  is  called  a  caryopsis.  That  of  the  Corn  is  one  of 
many  similar  fruits  aggregated  on  a  common  receptacle  popu- 
larly called  the  "cob."  The  so-called  "tassels"  of  the  Corn 
are  the  clusters  of  staminate  flowers;  the  "silks"  that  protrude 
from  the  young  "  ear"  are  the  styles  and  stigmas ;  the  "  kernels  " 
(fruits)  are  the  ripened  ovaries  ;  and  the  "  husks  "  are  bracts  which 
subtend  the  pistillate  inflorescence,  and,  persisting,  form  the  cover- 
ing of  the  fruits  until  they  are  ripe. 

There  are,  as  is  well  known,  a  great  many  different  kinds  of 
Maize,  but  all  of  them,  from  the  most  pigmy  varieties  of  "pop- 
corn "  to  the  giant  "  dent  corn,"  are  probably  but  varieties  of  a 
single  species. 

(1)  External  Characteristics. — In  the  larger  varieties  of  Field 
Corn — Yellow  Dent,  for  example — the  fruits  may  be  twelve  or 
fifteen  millimetres  long  by  ten  or  twelve  millimetres  wide  and 
five  or  six  millimetres  thick.  The  sides  are  more  or  less  flattened 
by  the  mutual  pressure  of  the  grains  during  growth.  On  one  of 

16  241 


242  LABORATORY    EXERCISES    IN    BOTANY. 

the  flat  faces  is  a  shallow  depression,  oval  or  ovate  in  outline, 
beginning  near  the  hilum  and  extending  about  two-thirds  the 
length  of  the  grain.  It  is  usually  lighter  in  color  than  the  rest, 
and  marks  the  position  of  the  embryo.  Thus  the  seed,  aside 
from  its  coats,  is  composed  of  a  large  quantity  of  albumen  against 
one  side  of  which  is  lodged  the  relatively  small  embryo.  The 
hilum-  and  micropyle-scars  are  located  at  one  end,  the  narrower 
one,  and  near  together,  and  since  the  body  of  the  seed  is  not 
bent,  it  is  anatropous. 

Plate  XXXVII.  (Fig.  1)  shows  a  kernel  of  Yellow  Dent  Corn 
about  twice  the  natural  size,  a  is  the  depression  in  which  lies  the 
embryo,  and  6  and  e  are  respectively  the  micropyle-  and  hilum- 
scars. 

(2)  Internal  Structure. — If  one  of  the  grains  be  soaked  for  a  few 
hours  in  tepid  water  to  facilitate  cutting,  and  a  vertical  section  be 
made  in  such  a  manner  that  it  passes  medially  through  the  em- 
bryo, the  structure  shown  in  Plate  XXXVII.  (Fig.  2)  will  be  re- 
vealed. At  the  top  is  a  depression,  shown  at  a  in  the  figure.  The 
exterior  membrane  is  the  pericarp-wall,  interior  to  which,  with- 
out any  intervening  space,  are  seen  the  rudimentary  seed-coats. 
At  c  is  the  dense  horny  albumen  whose  cells  are  closely  packed 
with  starch-grains,  and  at  6  a  less  dense  and  more  farinaceous 
portion.  At  d  is  shown  the  large  body  often  called  the  scutellum, 
much  larger  than  all  the  rest  of  the  embryo  put  together.  It  has 
by  some  been  regarded  as  a  part  of  the  axis,  but  it  is  really  an 
outgrowth  from  the  base  of  the  cotyledon,  and  should  therefore 
be  regarded  as  a  part  of  it.  It  almost  completely  enwraps  the 
rest  of  the  embryo  and  supplies  nutriment  for  its  growth,  absorb- 
ing the  food  materials  from  the  endosperm,  with  which  it  is  in 
contact.  The  cotyledon  proper  is  shown  at  m,  and  it  fits  over  the 
well-developed  plumule  like  a  candle-extinguisher.  The  plumule 
is  shown  at  e,  the  caulicle  or  axis  at/,  the  radicle  at  g,  and  the 
root-sheath  or  coleorhiza,  an  organ  not  occurring  except  in  mono- 
cotyledonous  embryos,  at  i. 

If  a  grain  be  allowed  to  germinate  until  the  radicle  and  plum- 
ule have  emerged  from  their  enclosure,  the  relation  of  parts  will 
be  understood  better.  Such  a  grain  is  shown  in  Figure  3  (PI. 
XXXVII.)-  The  root-sheath,  pierced  by  the  growing  radicle, 
is  shown  at  d;  at  e  adventitious  roots  destined  soon  to  replace 


STUDY   OF   MONOCOTYL   AND   DICOTYL   EMBRYOS.  243 

the  primary  root,  which  early  ceases  to  grow,  are  beginning  to 
emerge  from  the  scutellum ;  and  at  a  is  shown  the  plumule,  fast 
developing  into  a  leafy  shoot. 

Now,  what  are  the  most  essential  differences  between  dicotyl- 
edonous embryos,  such  as  have  already  been  studied,  and  mono- 
cotyledonous ones  like  that  of  Maize?  (1)  There  are  in  the 
former  two  opposite  and  usually  equal  cotyledons,  while  in  the 
latter,  if  more  than  one  leaf  be  developed  in  the  embryo,  they  are 
alternate,  and  the  one  lowest  down  on  the  axis  is  much  larger  and 
envelops  the  rest.  (2)  In  the  great  majority  of  monocotyledonous 
embryos  a  root-sheath  is  present,  but  not  in  dicotyledonous  ones. 
(3)  In  germination  the  portion  of  the  caulicle  below  the  cotyledon, 
called  the  hypocotyl,  does  not  elongate,  but  remains  short,  the 
growth  of  the  stem  in  length  being  due  chiefly  to  the  elongation 
of  that  portion  above  the  cotyledon,  called  the  epicotyl.  This  is 
expressed  by  saying  that  the  germination  is  endorhizal.  In  di- 
cotyledonous embryos,  on  the  other  hand,  the  hypocotyl  usually 
elongates  more  or  less,  often  very  considerably,  as  well  as  the  epi- 
cotyl. This  is  expressed  by  saying  that  the  germination  is  ex- 
orhizal.  (4)  The  germination  of  a  monocotyledonous  embryo 
gives  rise  to  a  stem  which,  near  its  base  at  least,  is  nearly  always 
obconical  in  form  ;  that  is,  the  larger  diameter  is  toward  the  apex 
rather  than  at  the  base,  the  reverse  of  what  it  is  in  the  stem  de- 
veloped from  a  dicotyledonous  embryo.  (5)  In  nearly  all  mono- 
cotyledonous embryos  the  primary  root  stops  growing  at  an  early 
period  after  germination,  and  in  some  instances  scarcely  develops 
at  all,  being  replaced  functionally  by  the  growth  of  lateral  or 
adventitious  roots.  These  sometimes  may  even  be  recognized  in 
the  embryo  before  germination.  In  dicotyledonous  embryos,  on 
the  other  hand,  the  primary  root  usually  persists  longer,  frequently 
throughout  the  life  of  the  plant,  giving  rise  to  huge  tap-roots  and 
an  extensive  root-system  of  which  it  is  the  axial  portion. 

These  differences  in  the  embryos  form  the  basis  of  the  division 
of  angiospermous  plants  into  two  great  sub-classes,  the  monocot- 
yls  and  the  dicotyls,  which  also  differ  from  each  other  in  many 
other  particulars  to  which  in  previous  Exercises  attention  has 
been  called — namely,  in  the  structure  of  their  roots,  in  the  struc- 
ture and  growth  of  their  stems,  in  the  venation  of  their  leaves, 
and  in  the  numerical  plan  of  their  flowers. 


244  LABORATORY    EXERCISES   IX    BOTANY. 

II.  A  SEED  HAVING  A  POLYCOTYLEDONOUS  EMBRYO. — The 
seeds  of  Pinus  mouophylla,  and  those  of  one  or  two  other  species 
of  Pine  from  the  Pacific  coast,  are  now  sometimes  seen  in  our 
markets  under  the  name  of  "  pifions,"  as  they  are  coming  to  be 
appreciated  as  articles  of  food. 

These  seeds,  like  those  of  all  other  members  of  the  Pine  fam- 
ily, are  borne  in  a  scaly  fruit  called  a  cone  or  strobile,  and  each 
seed  is  the  product  of  a  naked  ovule,  two  ovules  being  usually 
borne  on  the  inner  face  of  each  scale  of  the  cone.  The  name 
Gymnospermce  is  applied  to  the  great  class  of  plants  of  which  the 
Pines  are  the  most  conspicuous  and  important  members,  because 
the  ovules  are  exposed,  or  not  enclosed  by  a  carpellary  leaf  or 
leaves.  All  other  flowering  plants  are  grouped  in  one  class,  and 
this  is  called  Angiospermce,  because  the  ovules  are  enclosed  by  a 
carpellary  leaf  or  leaves.  Angiosperms,  in  other  words,  have 
ovaries,  while  gymuosperms  have  none. 

(1)  External  Characteristics. — The  seeds  of  Pinus  monophylla 
are  wingless,  oblong,  oval  or  ovate  in  outline,  somewhat  flattened 
on  one  or  more  sides,  and  more  or  less  pointed,  with  a  minute  scar, 
the  micropyle-scar,  at  one  end.     The  seed  is  often  faintly  marked 
by  two  narrow  longitudinal  ridges  on  opposite  sides,  usually  more 
distinct  near  the  narrower  end.     The  length  is  from  twelve  to 
sixteen  millimetres,  and  the  greatest  thickness  from  six  to  eight 
millimetres.     The  exterior  is  smoothish  and  brown. 

(2)  Internal  Structure. — Carefully  removing  the  hard  outer  coat 
of  the  seed,  the  nucellus  is  found  to  be  invested  in  a  thin,  mem- 
branous, reddish  inner  coat,  which   is   usually  more   distinctly 
marked  than  the  outer  by  the  longitudinal  ridges  already  re- 
ferred to.     Removing  this,  the  nucellus  is  observed  to  be  white, 
smooth,  and  perforated  at  the  micropylar  end  by  a  small  aperture. 

Cutting  the  nucellus  longitudinally  through  the  middle  of  this 
aperture,  it  is  found  to  be  composed  of  a  straight  embryo  imbedded 
axially  in  a  rather  copious  albumen,  as  shown  on  Plate  XXXVII. 
(Figs.  5  and  6).  The  embryo,  cut  longitudinally,  separated 
from  the  albumen,  and  magnified,  is  shown  on  Plate  XXXVII. 
(Fig.  7).  Attached  to  its  radicle  end  at  a  are  some  appendages 
of  cobwebby  appearance:  these  are  the  remains  of  the  suspensors 
and  of  other  embryos  which  have  failed  to  develop.  When  in 
their  natural  position  they  lie  in  a  cavity  of  the  albumen  at 


STUDY    OF    MONOCOTYL    AND    DICOTYL    EMBRYOS.  245 

the  radicular  end  of  the  embryo,  and  are  also  shown  on  Plate 
XXXVII.  (Fig.  6,  6).  At  b  (PI.  XXXVII.  Fig.  7)  is  the  rad- 
icle ;  at  c,  the  caulicle ;  at  d,  a  small  conical  prominence  repre- 
senting the  plumule,  though  it  consists  wholly  of  a  portion  of 
the  axis  (epicotyl),  no  leaves  being  as  yet  formed  upon  it ;  and  at 
e,  one  of  the  several  cotyledons.  These,  in  this  species,  range  in 
number  from  six  to  ten,  and  form  a  whorl. 

In  the  cross-section  of  the  seed,  shown  in  Figure  8  (PL 
XXXVII.),  the  section  passes  through  the  cotyledons  trans- 
versely. In  this  instance  they  are  nine  in  number,  arranged,  it 
will  be  seen,  in  a  circle.  A  minute  dot  is  perceptible  in  each 
cotyledon,  the  beginning  of  the  single  vein  that  traverses  it  when 
mature. 

Except  for  the  number  of  cotyledons,  this  embryo  is  in  all 
essential  respects  like  the  dicotyledonous  ones  already  studied.  In 
fact,  in  many  of  the  Gymnospermse  the  embryos  do  not  even  pos- 
sess this  difference,  having  but  two  cotyledons.  The  mode  of 
germination  is  also  essentially  like  that  of  dicotyledonous  embryos. 

Though  the  GymnospermaB  are  on  the  whole  lower  in  the  life- 
scale  than  either  monocotyls  or  dicotyls,  judging  by  their  embryos 
and  by  the  structure  of  their  steins,  which  are  closely  similar  to 
those  of  dicotyls,  one  may  conclude  that  they  are  more  nearly 
allied  to  the  latter  group  than  to  the  former. 

It  should  be  noted  that  there  are  a  few  cases  among  plants  that 
are  really  dicotyls  where  one  of  the  cotyledons  becomes  aborted, 
as  in  Abronia ;  in  some  other  rare  instances — as  in  Cuscuta,  for 
example — both  cotyledons  disappear ;  and  in  a  few  instances  also 
the  cotyledons  become  abnormally  multiplied,  or  polycotyledouous. 
Embryos  of  the  Lemon,  for  example,  have  been  seen  with  as  many 
as  four  cotyledons,  though  the  normal  number  is  two. 


STUDY   OF   MONOCOTYL   AND   DICOTYL    EMBRYOS.          247 


PLATE  XXXVII.,  FIG.  1.— A  Grain  of  Yellow  Dent  Corn  (about  twice  natural  size) :  a, 
depression  on  one  side,  in  which  lies  the  embryo ;  b,  micropyle  ;  c,  hilum. 

FIG.  2.— One  of  the  grains  in  longitudinal  section :  a,  depression  at  top  of  grain ;  6, 
lighter  and  less  dense  portion  of  endosperm ;  c,  denser  portion ;  d  and  h,  portions  of 
scutellum;  e,  plumule ; /,  axis  or  caulicle;  g,  radicle;  i,  root-sheath  or  coleorhiza;  m, 
cotyledon. 

FIG.  3.— A  Grain  of  Maize  in  process  of  germination :  a,  plumule ;  6,  portion  of  scutel- 
lum; c,an  adventitious  root;  d,  root-sheath  through  which  the  primary  root,  e,  has  burst. 

FIG.  4.— Seed  of  Pinus  monophylla  (enlarged  about  l]4  diameters). 

FIG.  5.— The  same  cut  longitudinally,  showing  internal  structure :  a,  outer  seed-coat;  &, 
inner  coat ;  c,  embryo ;  d,  albumen  ;  e,  micropyle. 

FIG.  6.— Nucellus  of  Seed  separated  from  the  seed-coats  and  laid  open  longitudinally: 
«,  opening  at  micropylar  end;  b,  remains  of  embryos  that  did  not  develop,  and  of  sus- 
pensory filaments  ;  c,  albumen  ;  d,  embryo. 

FIG.  7.— An  Embryo  removed  from  its  cavity  in  the  albumen  (considerably  magnified) : 
a,  suspensory  filaments  and  rudimentary  embryos;  6,  radicle  with  root-cap  already 
formed ;  c,  caulicle  ;  d,  conical  apex  of  the  stem ;  e,  one  of  the  several  cotyledons. 

FIG.  8.— Transverse  section  of  one  of  the  Seeds  cutting  through  the  Cotyledons :  a, 
outer  seed-coat ;  &,  one  of  the  cotyledons  ;  c,  albumen. 


FOKM  FOE  THE  STUDY  OF  SEEDS. 


I.  SIZE. 

(4)  Aril  entire. 

6.  Quantity. 

1.  Length. 
2.  Breadth. 

(5)  Aril  branching. 
(6;  Size  of  aril. 

Copious. 
Equal. 

3.  Thickness. 

a.  Large. 
b.  Small. 

Scanty. 
c.  Position. 

11.  COLOR. 

3.  Carunculate. 
(1)  Color  of  caruncle. 

Surrounding  embryo. 
Surrounded    by    em- 

1. Exterior. 

(2)  Caruncle  large. 

bryo. 

2.  Interior. 

(3)  Caruncle  small. 
4.  Atropous. 

To  one  side  of  embryo. 
d.  Texture. 

III.  SHAPE. 

5.  Campylotropous. 

Mealy. 

1.  Globose. 
2.  Discoid. 
3.  Lenticular. 
4.  Cylindrical. 
5.  Prismatic. 
6.  Pyramidal. 
7.  Three-sided. 
8.  Conical. 
9.  Ovoid. 
10.  Crescentic. 
11.  Ren  i  form. 
12.  Flattened. 
13.  Polyhedral. 

6.  Amphitropous. 
1.  Anatropous. 
8.  Shape  of  hilum-scar. 
(1)  Circular. 
(2)  Oblong. 
(3)  Linear. 
(4)  Curved. 
(5)  Triangular. 
(6)  Conspicuous. 
(7)  Inconspicuous. 
9.  Micropyle-scar. 
(1)  Conspicuous.  ** 
(2)  Inconspicuous. 
(3)  Adjacent  to  hilum. 

Oily. 
Horny. 
Bony. 
Containing  starch. 
Without  starch. 
(3)  Embryo, 
a.  Kind. 
Monocotyl. 
Dicotyl. 
Polycotyl. 
Acotyl. 
b.  Parts  recognizable. 
Radicle. 
Caulicle. 

14.  Lobed. 
15.  Nodular. 

(4)  At  opposite  end  from 
hilum. 

Cotyledons. 
Plumule. 

16.  Irregular. 

(5)  Midway  between  op- 

c. Position. 

posite     end     and 

Straight. 

IV.  SURFACE  AND   APPEND- 

hilum. 

Plicate. 

AGES. 

Curved. 

1.  Smooth. 

VI.  INTERNAL  STRUCTURE. 

Coiled. 

2.  Polished. 

Cotyledons. 

3.  Rugose. 

1.  Testa. 

Accumbent. 

4.  Reticulate. 

(1)  Homogeneous. 

Incumbent. 

5.  Alveolate. 

(2)  Differentiated      into 

Number. 

6.  Tuberculate. 

layers. 

Texture. 

7.  Scabrous. 

(3)  Texture. 

Membranous. 

8.  Verrucose. 

a.  Membranous. 

Thickish. 

9.  Pubescent. 

b.  Thick. 

Thick. 

10.  Puberulent. 

c.  Mucilaginous     ex- 

Shape. 

11.  Sericeous. 

teriorly. 

Linear. 

12.  Lanuginous. 
13.  Tomentose. 

d.  Fleshy. 
e.  Leathery. 

Oblong. 
Elliptical. 

14.  Villose. 

/.  Woody. 

Ovate. 

15.  Strigose. 

g.  Horny. 

Obovate. 

16.  Spinose. 

h.  Bony. 

Lanceolate. 

2.  Tegmen. 

Oblanceolate. 

V.  EXTERNAL  STRUCTURE. 

(1)  Membranous. 
(2)  Distinct. 

Clavate. 
Cordate. 

1.  Comose. 
(1)  Coma  at  hilum  only. 
(2)  Coma  at  hilum  and 

(3)  Coalescent  with  testa. 
(4)  Wanting. 
3.  Nuceltus. 

Lenticular. 
Irregular. 
Entire. 

along  raphe1. 
(3)  Coma  covering  most 
of  surface. 

(1)  Composition, 
a.  Exalbuminous. 
b.  Albuminous. 

Lobate. 
Composition. 
Starchy. 

2.  Arillate. 

(2)  Albumen. 

Without  starch. 

(1)  Color  of  aril. 

a.  Composition. 

Germination. 

(2)  Aril  tieshv. 
(3)  Aril  fibrous. 

Endosperm. 
Perisperm. 

Epigeal. 
Hypogeal. 

PART  II. 

VEGETABLE  HISTOLOGY. 


INTRODUCTION. 

THE  MICROSCOPE  AND  ACCESSORY  APPARATUS  TO  BE 
USED  IN  THIS  COURSE. 

THE  MICROSCOPE. 

THE  essential  parts  of  the  compound  microscope  are  the  fol- 
lowing : 

(1)  The  stand,  or  that  part  of  the  instrument  which  holds  in 
position  the  optical  parts  and  the  object  to  be  examined.  It  may 
be  quite  simple  or  very  complicated  in  its  construction,  according 
to  the  uses  to  be  made  of  it  or  the  fancy  of  the  user,  but  for  the 
purpose  of  these  exercises  a  simply-constructed  stand  is  preferable 
as  being  less  expensive,  more  readily  understood,  and  more  easily 
manipulated.  It  should,  however,  be  substantially  and  carefully 
made,  so  as  to  admit  of  the  use  of  high  powers  and  not  be  liable 
to  be  easily  disarranged.  A  stand  of  small  or  moderate  size,  built 
after  the  so-called  Continental  model,  is  preferable  for  botanical 
work  to  one  of  larger  size,  both  because  more  convenient  to  han- 
dle and  because,  on  account  of  the  frequent  application  of  test- 
reagents  to  tissues  undergoing  investigation,  the  stage  of  the 
instrument  must  be  horizontal,  which  necessitates  an  upright 
position  of  the  stand.  If,  therefore,  the  stand  were  a  large  one, 
to  work  with  it  would  be  both  inconvenient  and  tiresome.  There 
are  now  many  different  instruments  to  be  had,  answering  well 
the  requirements,  the  product  of  both  American  and  European 
factories. 

The  construction  and  the  parts  of  the  stand  are  best  understood 
by  reference  to  the  accompanying  illustration  (Fig.  2).  The  tube 
or  combination  of  tubes  holding  the  optical  parts  is  called  the 

249 


i-:\i-:i:<  [BE8    IN    IJOTANY. 

,  indicated  at  A  in  tin-  figure.  The  interior  tube  (/>'),  called 
tin-  tir'iir-fii/n-,  ~Iide-  -moothly  within  tin-  outer  for  the  purpo-e  of 
van-ing  the  diManoe  between  the  eye-piece  (0)  and  the  objective 
(6r),  wliieh  diMance  vane-  within  certain  limits  the  magnifying 
power  of  the  combination.  The  body  is  supported  by  an  (inn  (  /'') 
ri-jidlv  connected  with  the  staye  (IT).  At  D,  wliciv  the  body  is 
connected  with  the  arm,  is  a  rack  and  pinion  by  mean-  of  which 
the  body  may  be  raised  or  lowered.  This  constitutes  what  is 
called  the  coarse  adjustment,  and  it  should  be  constructed  with 
the  greatest  care  that  the  movements  be  smooth  and  true,  without 
liability  to  derangement.  The  coarse  adjustment  should  al-o  be 
so  constructed  as  to  compensate  for  wear,  and  the  rack  >hould  be 
Ion-  enough  to  permit  at  least  six  centimetres  working  distance 
between  the  stage  and  the  front  of  the  objective.  The  oblique 
rack-work  is  no  doubt  preferable  to  the  ordinary  form,  giving, 
when  well  constructed,  greater  steadiness  of  motion.  At  /•,'  is  tin- 
head  of  a  fine-threaded  screw  by  means  of  which  the  whole  body 
of  the  instrument  may  be  raised  or  lowered  very  gradually  through 
a  short  distance.  This  screw  is  used  in  focusing  with  high  powers, 
and  is  hence  called  the  fine  adjustment.  This  part  of  lh<-  inMrii- 
ment  also  requires  especial  care  in  its  construction,  so  that  lost 
motion  may  be  avoided  and  that  the  adjustment  may  not  easily  be 
impaired  by  use. 

The  stage  should  be  commodious — not  less  than  seven  centi- 
metres from  front  to  back,  and  not  less  than  eight  centimetres 
from  right  to  left.  The  upper  surface,  which  should  be  faced 
with  either  vulcanite  or  glass,  so  that  it  may  not  be  acted  upon  by 
corrosive  reagents,  should  be  very  rigid  and  firm,  and  ils  plane 
should  be  exactly  at  right  angles  to  the  optical  axis  of  the  inMrn- 
ment.  The  central  aperture,  through  which  light  is  admitted  from 
below  for  illuminating  the  object,  should  be  not  less  than  two  cen- 
timetres in  diameter.  This  aperture  should  be  provided  with  dia- 
phragm- for  regulating  the  light.  The  best  form  of  diaphragm, 
becan-e  the  most  convenient  in  adju-lment,  is  the  iris  diaphragm, 
<  )n  the  upper  surface  of  the  Mage  are  two  spring-clip-  for  holding 
the  object-slide  in  position. 

To  an  extension  of  the  arm  below  the  stage  is  attached  the 
///////////////////  mirror  (I).  This  should  have  a  diameter  of  about 
five  centimetres,  and  one  of  its  laces  should  be  plane,  the  other 


FH..  ii.— Continental  Microscope  (Bauscli  &  Louib  Optical  Co.). 


251 


252  LABORATORY    EXERCISES   IN    BOTANY. 

concave.  It  should  be  adjustable  to  any  angle,  and  be  suspended 
on  a  bar  which  is  both  capable  of  swinging  in  the  vertical  plane 
to  secure  either  direct  or  oblique  illumination,  and  extensible, 
so  that  the  concave  mirror  may  be  adjusted  for  the  use  of  either 
parallel  or  diverging  rays. 

As  an  addition  to  the  illuminating  apparatus  a  condenser  of  the 
Abbe  type  is  a  great  convenience,  though,  for  botanical  work,  not 
a  necessity. 

The  part  of  the  stand  which  supports  the  stage,  arm,  and  body 
with  the  optical  parts  is  called  the  pillar.  It  should  be  jointed 
as  shown  at  L,  so  as  to  permit  of  the  inclination  of  the  body  at 
any  angle.  The  pillar  in  turn  is  supported  by  a  heavy  piece  of 
metal  called  the  base  (K).  This  should  be  so  shaped,  and  the 
position  of  the  pillar  so  adjusted,  that  the  instrument  will  be  per- 
fectly steady  in  any  position  of  the  body  or  stage. 

Another  piece  of  apparatus  to  be  regarded  as  a  part  of  the  stand 
is  so  convenient  that  it  must  not  be  omitted  from  the  description  of 
a  stand  suitable  for  work  in  a  botanical  laboratory  :  this  is  a  double 
or  triple  nose-piece  for  holding  two  or  more  objectives. at  a  time. 
With  this  simple  revolving  arrangement  the  great  loss  of  time 
consequent  on  screwing  in  and  screwing  off  objectives,  as  well  as 
the  risk  of  breakage,  is  avoided. 

(2)  The  optical  parts  consist  of  two  kinds,  eye-pieces  and 
objectives. 

The  eye-piece,  as  the  name  implies,  is  the  lens  or  combination 
of  lenses  used  next  the  eye  of  the  observer,  and  indicated  at  C  in 
the  illustration.  In  its  ordinary  form,  the  Huygheuian,  it  con- 
sists of  two  plano-convex  lenses,  one  behind  the  other,  with  their 
plane  surfaces  toward  the  eye,  and  placed  at  a  distance  from  each 
other  equal  to  half  the  sum  of  their  focal  lengths.  The  lens  next 
the  eye  is  called  the  eye-lens,  that  farthest  away  from  it  the  field- 
lenSj  and  between  these,  in  the  focus  of  the  eye-lens,  is  a  dia- 
phragm to  shut  off  extreme  rays  and  such  others  as  may  be  re- 
flected from  the  sides  of  the  tube.  In  order  to  reduce  internal 
reflection  to  the  minimum,  the  interior  not  only  of  the  eye-piece 
tube,  but  also  that  of  all  others  through  which  the  rays  from  the 
front  lens  of  the  objective  pass,  is  painted  a  dead-black. 

The  eye-pieces  are  so  constructed  as  to  fit  rather  loosely  in  the 
eye-end  of  the  tube  and  to  be  readily  interchangeable.  Several 


INTRODUCTION.  253 

different  ones  may  be  used,  giving  different  magnifying  powers. 
The  common  mode  of  rating  them  is  by  their  focal  length.  The 
most  serviceable  are  the  two-inch,  the  one-aud-a-half-iuch,  and 
the  one-inch,  or,  if  German  or  French  microscopes  are  employed, 
the  Nos.  i.,  ii.,  and  iii.  eye-pieces. 

The  objectives  are  the  lenses  or  combinations  of  lenses  which 
screw  into  the  front  end  of  the  tube,  or  next  the  object,  whence 
the  name  objective.  One  is  shown  at  G  in  the  illustration.  As  a 
matter  of  fact,  the  objectives  of  all  really  serviceable  microscopes 
are  combinations  of  two  or  more  lenses  and  of  two  or  more  dif- 
ferent kinds  of  glass,  very  carefully  ground  and  polished  and  with 
their  curvatures  very  accurately  adjusted  each  to  the  other,  so  as 
to  give  a  clear  and  faithful  image  of  the  object — a  result  which 
could  not  be  accomplished  by  means  of  a  single  lens.  Objectives 
require,  therefore,  great  skill  in  their  manufacture,  and  constitute 
the  most  expensive  parts  of  the  microscope.  This  is  especially 
true  of  the  high  powers,  where  the  combinations  must  be  very 
complex  in  order  to  give  the  most  perfect  results. 

Objectives  of  many  different  powers  are  manufactured,  and 
these  too  are  rated  according  to  their  equivalent  focal  length. 
The  most  serviceable  for  botanical  purposes  are  a  one-inch  or  a 
two-third-iuch  for  a  low  power  and  a  one-sixth-inch  or  a  one- 
eighth-inch  for  a  high  power.  These,  with  the  eye-pieces  men- 
tioned, will  permit  of  a  range  of  powers  from  about  forty  or 
fifty  diameters  to  six  hundred  or  eight  hundred  diameters — 
amply  sufficient,  if  the  objectives  are  of  good  quality,  for  most 
of  the  work  that  needs  to  be  done  by  the  student  of  vegetable 
histology. 

(3)  Estimation  of  Magnifying  Power. — The  magnifying  power  of 
a  compound  microscope  may  be  roughly  calculated  as  follows  :  Sup- 
pose the  tube  to  be  of  such  a  length  that  the  distance  in  a  straight 
line  from  the  object  when  in  focus  to  the  distal  end  of  the  eye- 
piece is  ten  inches,  and  that  the  two-inch  eye-piece  and  the  one- 
inch  objective  are  in  position.  Ten  inches  being  the  normal  length 
of  distinct  vision,  an  objective  that  focuses  an  object  at  one-inch 
distance  practically  brings  it  ten  times  nearer,  and  therefore  mag- 
nifies it  ten  diameters.  The  same  reasoning  applies  to  the  eye- 
piece, which  magnifies  the  image  produced  by  the  objective,  and, 
as  the  eye-piece  in  this  case  magnifies  five  diameters,  the  magni- 


'2~>  \  LABORATORY    EXERCISES   IN  .BOTANY. 

ficatiou  produced  by  the  combination  is  five  times  ten,  or  fifty, 
diameters. 

In  like  manner,  other  conditions  remaining  the  same,  if  there 
be  substituted  for  the  optical  parts  just  mentioned  the  one-inch 
eye-piece  and  the  one-eighth-iuch  objective,  the  magnification 
will  be  eight  hundred  diameters. 

If,  without  changing  the  optical  parts,  the  tube  of  the  micro- 
scope be  lengthened,  the  magnification  of  the  objective  will  be  in- 
creased ;  if  the  tube  be  shortened,  the  magnification  will  be  de- 
creased ;  and  the  magnifying  power  of  the  combination  will  be 
increased  or  decreased  in  nearly,  though  not  quite,  the  same 
proportion. 

Since,  however,  the  objectives  and  the  eye-pieces  are  not  always 
correctly  rated  by  their  makers,  a  more  exact  way  of  determin- 
ing the  magnifying  power  of  the  different  combinations  is  by 
measuring  them  directly  by  means  of  a  stage  micrometer  and  a 
camera  lucida.  The  stage  micrometer  consists  of  a  very  fine  scale 
accurately  ruled  on  a  glass  slide  or  cover-glass.  This  is  placed  on 
the  stage  and  the  microscope  focused  upon  the  lines.  The  camera 
lucida  is  then  placed  in  position  on  the  eye-piece,  when  the  lines 
may  be  seen  projected  on  a  sheet  of  paper  placed  beside  the  micro- 
scope, and  their  image  may  be  drawn.  That  the  result  may  be 
correct,  the  drawing-paper  must  be  placed  at  right  angles  to  the 
direction  in  which  the  object  is  seen  by  the  eye,  and  at  the  same 
distance  from  it  as  the  micrometer  lines  on  the  stage.  Suppose, 
as  a  practical  example,  that  the  lines  on  the  micrometer  are  known 
to  be  precisely  one-one-hundredth  millimetre  apart,  while  those 
in  the  magnified  drawing  made  of  them  are  five  millimetres 
apart;  what  is  the  magnifying  power  of  the  combination  used? 
The  question  is  easily  answered,  for,  clearly,  the  apparent  dis- 
tance measured  is  just  five  hundred  times  as  great  as  the  real  dis- 
tance between  the  lines;  the  magnifying  power  must  therefore  be 
five  hundred  diameters. 

It  is  not  even  necessary  to  employ  a  camera  lucida  for  the  pur- 
pose of  determining  the  magnification  unless  results  of  great 
precision  are  required.  It  may  be  done  with  a  close  approxima- 
tion to  accuracy  with  no  other  apparatus  than  a  good  stairr  microm- 
eter and  a  foot-rule,  by  the  following  process:  Focus  the  microm- 
eter on  the  stage,  and  place  beside  the  latter,  on  the  same  level 


INTRODUCTION.  255 

as  the  micrometer  and  parallel  to  its  scale,  the  foot-rule,  prefera- 
bly one  having  a  white  surface  ruled  with  black  lines,  and  then 
look  with  one  eye  through  the  microscope  at  the  scale  on  the  stage, 
at  the  same  time  keeping  the  other  eye  open.  Both  scales  will  be 
seen  simultaneously,  and  may  be  directly  compared. 

Suppose,  for  example,  that  the  lines  on  the  micrometer  scale, 
which  are  known  to  be,  say,  one-one-thousandth  of  an  inch  apart, 
appear  through  the  microscope  to  be  precisely  one  inch  apart  as 
measured  by  the  foot-rule :  the  magnifying  power  used  must 
therefore  be  one  thousand  diameters. 

ACCESSORY  APPARATUS. 

The  following  may  be  regarded  as  necessities : 

(1)  A  stage  micrometer,  preferably  one  ruled  according  to  the 
metric  scale.     One  millimetre  ruled  into  one  hundred  equal  parts 
is  a  very  convenient  scale  for  most  purposes. 

(2)  A  section  knife  for  making  thin  sections  of  tissues.     The 
most  convenient  for  ordinary  work  is  a  good  razor  ground  flat  on 
one  side  and  slightly  concave  on  the  other,  but  not  too  thin,  and 
with  a  straight  edge.     It  should  be  kept  well  sharpened,  and  the 
student  would  do  well  to  provide  himself  also  with  a  good  hone 
and  strop. 

(3)  A  graduated  ruler  such  as  the  one  described  above,  or  pref- 
erably one  with  the  English  scale  on  one  edge  and  the  metric 
scale  on  the  other.     Such  a  ruler  is  highly  useful  not  only  for  the 
purpose  above  mentioned,  but  also  in  drawing. 

(4)  A  pair  of  dissecting-needles.      These  may  easily  be  made 
from  two  cedar-wood  pen-holders  by  sawing  them  off  through 
the   metallic  portion  so  that  the   remaining   metal  will  form  a 
ferule,  and  then,  by  means  of  pincers,  forcing  the  heads  of  sew- 
ing-needles into  the  feruled  ends.     These  needles  are  very  useful 
for  teasing  apart  tissues  that  have  been  treated  with  Schulze's 
maceration  fluid. 

(5)  A  pair  of  sharp-pointed  scissors  for  dividing  sections,  mem- 
branous tissues,  etc.     Bent  ones,  such  as  those  shown  in  Figure  3, 
are  to  be  preferred. 

(6)  A  pair  of  delicate  forceps  or  pincettes  for  handling  cover- 
glasses  and  small  objects.     A  very  good  form  for  laboratory  pur- 
poses is  shown  in  the  illustration  (Fig.  3). 


256 


LABORATORY    EXERCISES    IN    BOTANY. 


(7)  A  supply  of  watch-glasses.  These  are  for  containing  sec- 
tions during  the  processes  of  bleaching,  staining,  etc.  The  ordi- 
nary kinds  of  curved  glasses,  such  as  are  readily  procurable  at 


FIG.  3. — Curved  Scissors  and  Forceps  (Bausch  &  Lomb  Optical  Co.). 

any  watchmaker's,  may  be  used,  or,  better,  those  made  especially 
for  microscopic  purposes,  and  sold  under  the  name  of  "  Syracuse 
solid  watch-glasses."  These  are  usually  sold  in  nests  of  six  with 
a  stand  for  holding  them. 

(8)  A  small  porcelain  evaporating-dish  for  use  in  macerating 
sections  with  Schulze's  maceration  fluid. 

(9)  One    dozen    capped  reagent-bottles, 
such    as    that   shown     in   the     illustra- 
tion  (Fig.  4),  and   three   or  four  acid- 
bottles  each  of  about  one  ounce  capac- 
ity.     The  capped   bottles   should    each 
be  provided  with  a  small  glass  tube  or 
pipette. 

(10)  A  supply  of  camel' s-hair  brushes. 
A    half  dozen,   assorted    sizes,  are   suf- 
ficient.     They   are   useful    in    handling 
sections  and  in  finishing  slides. 

(11)  A  supply  of  glass  slides  for  mount- 
ing objects.    They  should  be  of  regulation 
size,  three  inches  by  one  inch,  of  clear, 
well-polished  glass,  have  ground  od^vs, 
and   should   not  be   too   thick.       Those 

about  one  millimetre  in  thickness  are  to  be  preferred. 

(12)  A  supply  of  thin  cover-glasses.     Three-quarter-inch  circles, 
No.  2,  are   suitable  for   most  purposes,    but   it  would    be    well 


FIG.  4.— Capped  Reagent- 
bottle. 


INTRODUCTION. 


257 


also  to  have  a  few  of  larger  size,  seven-eighths  of  an  inch  in 
diameter. 

The  following  pieces  of  apparatus,  though  useful,  are  not  really 
indispensable  for  such  a  course  as  here  laid  down  : 

(a)  A  camera  lucida  for  drawing.     The  most  useful  form  is 
that  devised  by  Professor  Abbe,  and  now  manufactured  under 
various  modifications  by  most  of  the  principal  makers  of  micro- 
scopes.    The  principle  of  its  construction  is  explained  and  illus- 
trated in  the  author's  College  Botany,  pp.  206,  207.      There  are 
several  cheaper  kinds,  but  this  is  altogether  the  most  desirable. 

(b)  A  polariscope  is  a  useful  adjunct  to  the  microscope  in  the 
investigation  of  certain  structures,  as  starches,  crystals,  thickened 
cell-walls,  etc.      It  consists  of  two  Nicol  prisms,  one   usually 
screwed  into  the  nose-piece  just  above  the   objective,  and  the 
other  arranged  to  rotate  beneath  the  stage. 


FIG.  5.— Student's  Microtome  (Queen  &  Co.). 

(c)  A  pair  of  draughtsman's  dividers  is  a  useful  implement  as  an 
aid  in  drawing  microscopic  objects. 

(d)  A  microtome  for  cutting  thin  and  even  sections  of  plant 
structures  is  useful,  and  for  some  of  the  more  difficult  investigations 


258 


LABORATORY    EXERCISES   IN    BOTANY. 


where  serial  sections  are  required  it  is  indispensable.  For  the 
latter  purpose  one  of  the  numerous  forms  of  the  sledge  microtome 
is  probably  on  the  whole  the  most  desirable ;  but  for  the  ordinary 
work  of  sectioning  stems,  roots,  leaves,  etc.  the  simple  and  inex- 
pensive sectioner  shown  in  Figure  5,  and  devised  in  accordance 
with  the  author's  suggestions,  is  very  convenient  and  efficient. 
It  is  a  modification  of  the  well  microtome,  the  novel  feature  in 
which  consists  in  the  manner  in  which  the  object  is  clamped  in 
the  well  so  as  to  prevent  it  from  bending  or  yielding  before  the 
knife.  It  is  made  of  such  a  form  as  to  be  conveniently  held  in 
one  hand  while  the  knife  is  manipulated  with  the  other.  The 
accompanying  illustration  will  give  an  idea  of  its  appearance  and 
the  method  of  using  it. 


FIG.  6.— Centring  Turn-table  (Zentmayer). 

(e)  A  turn-table  is  a  very  useful  bit  of  apparatus  for  the  per- 
manent mounting,  particularly  the  finishing,  of  slides.  Some  of 
the  self-centring  kinds  are  particularly  convenient.  One  of  these 
is  shown  in  the  accompanying  illustration. 

MICRO-REAGENTS. 

Sulphuric  Acid. — The  strong  acid  dissolves  starch  and  cellulose, 
causing  them  first  to  swell  and  then  to  disappear.  It  also  pro- 
duces chemical  change  in  them,  converting  the  former  into  dex- 
trin and  the  latter  into  amyloid,  a  substance  which,  like  starch, 
acquires  a  blue  color  with  iodine.  It  dissolves  protoplasm  and 
other  albuminous  substances  much  more  slowly,  and  hence  may 


INTRODUCTION.  259 

be  used  for  demonstrating  the  continuity  of  protoplasm  from  cell 
to  cell  in  certain  tissues.  For  this  purpose  it  is  used  either  strong 
or  diluted  with  one-fourth  its  bulk  of  water.  After  acting  for 
a  few  moments  the  acid  is  washed  out  thoroughly  and  the  sections 
are  stained. 

Cuticularized  and  lignified  tissues,  if  first  treated  with  iodine 
solution  and  then  with  sulphuric  acid  to  which  one-fourth  its  bulk 
of  water  has  been  added,  turn  brown,  but  the  former  are  not  dis- 
solved, and  the  latter  are  dissolved  much  more  slowly  than  are 
cellulose  tissues. 

Cells  containing  protoplasm,  if  first  treated  with  a  solution  of 
cane-sugar  and  then  with  dilute  sulphuric  acid,  acquire  a  rose-red 
color. 

In  the  dilute  form  sulphuric  acid  is  also  used  as  an  aid  to  the 
identification  of  certain  crystalline  deposits  in  cells,  crystals  of 
calcium  oxalate,  calcium  carbonate,  calcium  phosphate,  and  cal- 
cium malate  being  changed  to  needle-like  crystals  of  calcium  sul- 
phate in  the  cells.  Sphere  crystals  of  inulin  may  also  readily  be 
distinguished  from  those  of  calcium  phosphate  by  the  fact  that 
the  former  readily  dissolve  in  sulphuric  acid  without  residue. 

Sulphurous  Acid. — Certain  objects  when  hardened  in  alcohol 
turn  black,  and  sections  become  too  opaque  for  study.  To  prevent 
this,  Overton  adds  to  the  alcohol  sulphurous  acid  and  prepares 
the  hardening  solution  as  follows :  He  adds  to  half  a  gram  of 
sodium  sulphite  a  few  cubic  centimetres  of  80  per  cent,  sulphuric 
acid,  and  conducts  the  fumes  of  sulphurous  acid  which  are  gen- 
erated directly  into  100  grams  of  alcohol.  Sulphurous  acid  may  be 
employed  in  the  same  manner  in  picric-acid  hardening  solutions. 

A  weak  aqueous  solution  of  sulphurous  acid  also  greatly  expe- 
dites the  washing  of  tissues  which  have  been  hardened  in  chromic- 
acid  solutions. 

Hydrochloric  Acid. — Besides  its  use  in  connection  with  phloro- 
glucin,  phenol,  thymol,  a-naphthol,  and  anilin  chloride  as  a  reagent 
for  lignified  tissue,  hydrochloric  acid  is  more  or  less  useful  as  a 
clearing  agent.  It  is  also  serviceable  in  distinguishing  between 
calcium  carbonate  and  calcium  oxalate  in  cells,  both  being  soluble 
in  this  reagent,  but  the  former  with  effervescence,  the  latter  more 
slowly  and  without  effervescence. 

A  J  per  cent,  solution  of  hydrochloric  acid  in  70  per  cent,  alco- 


260  LABORATORY    EXERCISES   IN   BOTANY. 

hol  is  also  serviceable  in  reducing  the  color  of  sections  which  have 
been  over-stained  in  haematoxyliu,  carmine,  and  some  aniline 
solutions. 

Nitric  Acid. — The  strong  acid  immediately  kills,  but  does  not 
dissolve,  protoplasm,  and  causes  it  to  shrink  away  from  the  cell- 
wall.  If  a  solution  of  ammonium  or  potassium  hydrate  be  after- 
ward added,  the  proteid  cell-contents  will  assume  a  yellow  color. 
This  is  called  the  xantho-proteid  reaction  for  proteid s. 

If  a  section  containing  thick-walled  tissues  be  treated  first  with 
hot  nitric  acid  and  then  with  ammonia,  the  middle  lamella  will  be 
stained  yellow. 

A  solution  of  3  parts  of  strong  nitric  acid  in  97  parts  of 
water  is  sometimes  employed  for  fixing  protoplasm  where  it  is 
desired  to  study  the  microsomes  and  other  granular  contents. 

A  30  per  cent,  solution  of  nitric  acid  is  used  for  the  detection 
of  amyloid,  which  at  once  swells  strongly  when  the  reagent  is 
applied,  and  after  a  time  completely  dissolves. 

Chromic  acid  is  employed  in  .5  percent,  to  1  per  cent,  solutions 
for  fixing  the  cell-contents  of  tissues.  Tissues  are  soaked  in  it  for 
twenty-four  hours  or  more,  and  must  then  be  washed  thoroughly 
before  staining,  as  the  presence  even  of  traces  of  the  acid  inter- 
feres with  most  stains. 

A  concentrated  aqueous  solution  of  chromic  acid  is  often  em- 
ployed for  the  separation  of  cells,  especially  those  of  thick-walled 
tissues,  since  the  middle  lamella  is  more  readily  soluble  in  it  than 
is  the  rest  of  the  cell-wall.  All  cell-wall  structures  are,  however, 
finally  dissolved  by  it.  Suberized  and  cutinized  tissues,  though, 
yield  to  its  action  only  after  a  long  time.  Fungus  cellulose  also 
dissolves  very  slowly  in  it. 

Acetic  Acid  (Glacial). — This  acid  in  1  or  2  per  cent,  aqueous 
solution  is  serviceable  for  defining  the  nucleus.  It  is  also  used 
for  the  same  purpose  in  connection  with  certain  stains,  especially 
gentian-violet  and  methyl-green.  In  strong  solution  it  is  a  valu- 
able clearing  agent,  rendering  the  cell-contents  more  transparent 
and  the  cell-walls  therefore  more  distinct. 

A  mixture  of  acetic  acid  1  part  and  absolute  alcohol  3  parts 
forms  an  excellent  reagent  for  fixing  cell-contents  with  the  view 
to  subsequent  staining  and  study  of  the  nuclear  figures.  This 
mixture  is  also  useful  in  distinguishing  between  crystals  of  eal- 


INTRODUCTION.  261 

cium  oxalate  and  those  of  calcium  carbonate,  the  former  being 
insoluble  in  it,  while  the  latter  dissolve  with  effervescence. 

Formic  acid  is  employed  in  much  the  same  way  as  is  acetic 
acid  for  the  study  of  the  nucleus  and  for  clearing,  and  has  about 
the  same  value. 

Picric  Acid. — Strong  solutions,  either  aqueous  or  alcoholic,  are 
employed  for  fixing  the  cell-contents.  Objects  should  remain  in 
the  solution  from  twelve  to  twenty-four  hours,  and  should  then  be 
washed  thoroughly  in  alcohol  before  staining. 

Picric  acid  is  also  used  for  the  same  purpose  in  association  with 
sulphuric  acid :  2  parts  of  the  latter  are  mixed  with  100  parts  of 
water,  and  the  mixture  saturated  with  picric  acid  ;  the  whole  is 
then  mixed  with  three  times  its  volume  of  water.  This  solu- 
tion has  the  advantage  of  being  more  readily  washed  out  of  the 
tissues  by  alcohol  than  that  of  picric  acid  alone. 

By  reason  of  its  staining  as  well  as  its  fixing  properties  picric 
acid  is  used  also  in  association  with  carmine,  nigrosin,  and  ani- 
line-blue in  the  preparation  of  various  structures  for  study. 

Osmic  Acid. — This  poisonous  substance  owes  its  chief  value  in 
microscopy  to  the  fact  that  it  very  rapidly  penetrates  tissues  and 
instantly  kills  and  fixes  protoplasm.  It  is  quite  useful,  therefore, 
in  the  study  of  nuclear  figures.  It  is  often  employed  for  the  pur- 
pose in  1  per  cent,  solution  in  distilled  water.  The  treatment  of 
the  tissues  with  this  reagent  must  be  carried  on  in  the  dark,  and 
the  acid  must  be  washed  out  thoroughly  before  exposing  the  tis- 
sues to  the  light,  otherwise  reduction  to  the  metallic  form  will 
take  place  and  the  tissues  will  be  blackened.  This  reduction 
always  occurs  when  the  acid,  in  contact  with  organic  matter,  is 
exposed  to  light.  Tannins  and  fats  also  reduce  osmic  acid  with- 
out the  aid  of  light,  and  the  acid  may  therefore  aid  in  the  detec- 
tion of  these  substances. 

Sections  which  have  been  blackened  by  osmic  acid  may  be 
bleached,  without  injury  to  the  structure,  by  means  of  hydrogen 
peroxide,  which  may  be  used  in  the  proportion  of  1  part  to  10  or 
15  of  75  per  cent,  alcohol.  The  sections  may  then  be  washed 
and  stained. 

Osmic  acid  is  usually  sold  in  sealed  glass  tubes  containing  1  gram 
of  the  crystals.  To  prepare  the  solution  the  distilled  water  is  meas- 
ured out  and  poured  into  a  suitable  vessel,  and  then,  by  means  of 


262  LABORATORY    EXERCISES   IN   BOTANY. 

pincers,  the  tube  containing  the  acid  is  broken  beneath  the  surface 
of  the  liquid.  This  is  done  to  avoid  danger  of  poisoning.  The 
fumes  should  be  respired  as  little  as  possible. 

Phenol,  or  Carbolic  Add. — This  is  a  useful  clearing  agent.  For 
this  purpose  a  95  per  cent,  solution  of  the  crystals  in  water  is  pre- 
pared, and  the  sections  are  allowed  to  stand  in  it  for  a  time.  The 
clearing  is  hastened  by  the  application  of  heat.  Specimens  cleared 
in  carbolic  acid  may  be  mounted  directly  in  balsam,  anhydration 
being  unnecessary. 

Carbolic  acid  is  also  used,  in  association  with  potassium  chlorate 
and  hydrochloric  acid,  as  a  test  for  lignified  tissue,  a  blue  or  green- 
ish-blue color  being  produced  in  lignified  membranes  by  the 
reagent. 

Potassium  Hydrate. — This  is  one  of  the  most  useful  of  reagents. 
Its  value  depends,  in  the  main,  on  its  solvent  effects  upon  proteid 
matters  and  starch,  and  on  its  power  to  cause  cell- walls  to  swell, 
thus  rendering  their  structure  more  evident.  It  is  best  obtained 
in  sticks,  and  should  be  kept  in  tightly-stopped  bottles  until  re- 
quired for  use,  as  on  expbsure  it  takes  up  carbon  dioxide  and 
water  from  the  air  and  becomes  converted  into  a  solution  of  potas- 
sium carbonate.  When  a  solution  is  required  for  use,  remove  a 
small  piece  from  the  bottle,  dip  it  for  a  moment  in  water  to  remove 
the  film  of  carbonate,  and  dissolve  the  remainder  in  a  fresh  por- 
tion of  distilled  water.  For  some  purposes  a  dilute  solution  is  to 
be  preferred,  for  others  a  strong  one.  For  the  purpose  of  clearing 
tissues  a  5  to  10  per  cent,  solution  will  usually  suffice,  and  the 
best  results  are  obtained  by  allowing  the  tissues  to  remain  in  the 
fluid  for  some  hours.  The  sections  should  then  be  washed  in 
clean  water,  and  the  remaining  alkali  be  neutralized  with  dilute 
acetic  acid  before  placing  the  sections  under  the  microscope. 

For  the  study  of  the  markings  on  starch-grains  only  a  very 
weak  solution  should  be  employed.  The  lamination  of  thickened 
cell-walls  is  often  brought  out  very  distinctly  by  soaking  the  sec- 
tions for  a  few  hours  in  a  5  per  cent,  solution  of  the  alkali. 

In  concentrated  solution  potassium  hydrate  is  one  of  the  best 
reagents  for  the  identification  of  suberized  tissue,  which  is  colored 
yellow  by  it.  The  color  is  deepened  by  gently  heating,  and  if 
heated  to  boiling  the  suberin  exudes  from  the  cell-walls  in  the 
form  of  yellow  drops. 


INTRODUCTION.  263 

Tannin  may  also  be  recognized  by  a  strong  solution  of  the  re- 
agent, the  cell-contents  of  cells  containing  tannin  turning  yellow- 
ish or  brownish.  In  dilute  form  potassium  hydrate  may  also  be 
used  as  a  means  of  distinguishing  between  protein-crystals  or  crys- 
talloids and  crystals  of  inorganic  matters.  The  former  immediately 
swell  and  lose  their  angles,  while  the  latter  are  mostly  unaffected. 

Very  hard  tissues,  such  as  the  shells  of  many  nuts  and  the  ex- 
terior coats  of  many  seeds,  may  be  softened  for  sectioning  by  soak- 
ing them  for  some  time  in  solutions  of  this  reagent.  (For  soften- 
ing tissues  by  means  of  potassium  hydrate,  see  Introduction  to 
Part  I.). 

Potassium-iodide  Iodine. — This  is  one  of  the  most  useful  of  the 
solutions  employed  in  vegetable  histology.  It  stains  starch  blue, 
proteid  matters  yellowish-brown,  and  lignified  cell-walls  a  deep- 
brown.  Along  with  sulphuric  acid  it  may  also  be  used  as  a  test 
for  cellulose,  as  follows :  The  sections  are  first  treated  with  a  few 
drops  of  the  iodine  solution,  and  then,  after  a  few  minutes,  with 
a  mixture  of  2  parts  of  strong  sulphuric  acid  and  1  part  of  water. 
After  treatment  with  the  acid  the  cellulose  membranes,  which  are 
scarcely  stained  at  all  by  the  iodine  alone,  rapidly  acquire  a  blue 
color,  while  the  lignified  cell- walls  are  stained  a  deep-brown.  The 
iodine  solution  used  for  this  purpose  should  consist  of  iodine  1 
part,  potassium  iodide  4  parts,  and  distilled  water  195  parts. 

As  a  test  for  protoplasm  it  is  better  to  use  a  stronger  solution, 
in  order  that  the  staining  effects  may  be  decided,  but  as  a  test  for 
starch  the  solution  should  be  much  weaker,  otherwise  the  grains 
will  be  so  deeply  stained  as  to  appear  black.  Iodine  solution  also 
rapidly  kills  protoplasm  without  dissolving  it,  and  is  therefore 
useful  as  a  fixing  agent.  Vapor  of  iodine  is  sometimes  employed 
for  the  same  purpose. 

Alt  iodine  solutions  should  be  kept  in  amber-colored  bottles  to 
prevent  the  formation  of  iodic  acid. 

Chloriodide-of-zinc  Iodine  Solution*^- According  to  Behrens, 
this  solution  may  be  prepared  conveniently  by  dissolving  25  parts 
of  pure  zinc  chloride  and  8  parts  of  potassium  iodide  in  8.5  parts 
of  distilled  water  and  then  adding  as  much  iodine  as  will  dissolve. 

Solid  chloriodide  of  zinc  is,  however,  now  an  article  of  com- 
merce, and  a  still  simpler  way  of  making  the  solution,  according 
to  Zimmermann,  is  to  dissolve  the  salt  in  somewhat  less  than  its 


264  LABORATORY    EXERCISES    IN    BOTANY. 

own  weight  of  water,  and  then  add  a  quantity  of  metallic  iodine 
sufficient  to  give  the  solution  a  deep  sherry-brown  color. 

This  reagent  is  highly  useful.  It  constitutes  one  of  the  best 
direct  tests  for  cellulose,  coloring  it  blue,  while  lignified  and  cu- 
tinized  tissues  are  colored  brown.  Starch-grains  are  also  stained 
blue  by  it,  and,  besides,  are  caused  to  swell  and  finally  to  disap- 
pear. It  is  useful  in  the  study  of  sieve-tubes,  since  it  stains  cal- 
lose  a  deep-reddish  or  reddish- brown  color.  It  has,  moreover,  been 
employed  with  success  in  studying  the  continuity  of  protoplasm 
from  cell  to  cell,  since  it  swells  the  cell-walls  and  stains  the  proto- 
plasmic threads  brown. 

Chloral-hydrate  Iodine. — This  consists  of  5  parts  of  chloral 
hydrate  dissolved  in  2  parts  of  water  to  which  a  little  iodine  solu- 
tion has  been  added.  It  is  employed  for  dissolving  chlorophyll 
bodies  and  to  demonstrate  the  presence  in  them  of  minute  starch- 
grains  by  causing  the  latter  to  swell  and  by  staining  them  blue. 

The  solution  without  the  iodine  is  also  a  useful  clearing  agent, 
especially  for  rendering  leaves  transparent  after  the  chlorophyll 
has  been  dissolved  out  by  alcohol. 

Alcohol  has  many  important  uses  in  vegetable  histology.  One 
of  the  most  important  is  for  the  preservation  of  tissues.  For  this 
purpose  70  per  cent,  alcohol  is  strong  enough.  But  it  is  often 
desirable  at  the  same  time  to  harden  the  tissues  preparatory  to 
section-cutting.  For  this  purpose  strong  alcohol,  95  to  98  per 
cent.,  is  often  necessary.  If,  however,  the  tissues  are  very  deli- 
cate, they  must  not  be  placed  immediately  in  alcohol  of  this 
strength,  but  must  gradually  be  transferred  through  the  medium 
of  solutions  of  increasing  strength,  otherwise  osmotic  action  will 
contract  the  tissues  and  render  them  unfit  for  study. 

Alcohol  dissolves  chlorophyll  and  other  coloring  matters,  to- 
gether with  resinous  substances  and  some  oils,  and  so  acts  as  a 
bleaching  agent. 

Since  it  coagulates  and  kills  protoplasm  without  seriously  im- 
pairing its  structure,  alcohol  is  useful  in  preparing  cells  for  the 
study  of  the  cell-contents.  Living  protoplasm  is  so  transparent 
as  to  be  nearly  invisible,  and  it  is  also  very  difficult  to  stain  ;  but 
by  treatment  with  alcohol  protoplasm  is  rendered  more  opaque, 
and,  besides,  may  then  readily  be  stained  with  most  of  the  usual 
staining  fluids. 


INTRODUCTION.  265 

As  a  means  of  an hyd rating  tissues  preparatory  to  mounting  them 
in  Canada  balsam  or  other  resinous  mounting  media,  alcohol  is  in- 
dispensable, and  for  this  purpose,  of  course,  very  strong  or  abso- 
lute alcohol  must  be  employed. 

The  presence  of  inuliii  in  tissues  may  be  demonstrated  by 
the  use  of  alcohol.  Tissues  containing  inulin  may  be  soaked  in 
strong  alcohol  for  seven  or  eight  days,  during  which  the  iuuliu 
will  crystallize  in  the  cells  and  in  the  intercellular  spaces,  and  may 
be  seen  in  the  form  of  sphere  crystals. 

Sulphuric  Ether. — This  is  chiefly  used  as  a  solvent  for  fats  in 
the  study  of  such  organs  as  seeds,  which  often  contain  oily  mat- 
ters in  abundance.  It  is  also  useful  as  a  solvent  for  resins  and  for 
eerie  acid. 

Mercuric  Chloride. — This  is  a  valuable  fixing  agent,  as  it  rap- 
idly coagulates  protoplasm.  A  saturated  solution  in  distilled 
water  may  be  employed,  or  a  5  or  10  per  cent,  alcoholic  solution, 
or,  better  still,  a  saturated  solution  in  5  per  cent,  acetic  acid,  as 
this  penetrates  more  rapidly.  Objects  immersed  in  a  mercuric- 
chloride  solution  should  not  be  of  large  size,  nor  should  they  re- 
main in  it  longer  than  necessary  to  coagulate  the  albumens,  for 
the  tendency  of  the  liquid  is  to  render  the  tissues  brittle,  making 
them  difficult  to  section.  After  fixing,  the  objects  should  be  washed 
thoroughly  in  70  per  cent,  alcohol  to  get  rid  of  the  sublimate. 
They  may  be  sectioned  and  stained  by  the  usual  methods. 

Millon's  Reagent. — This  is  prepared  by  dissolving  metallic  mer- 
cury in  its  weight  of  concentrated  nitric  acid  and  diluting  the 
solution  with  an  equal  volume  of  distilled  water.  The  solution 
does  not  keep  long,  and  therefore  should  be  employed  only  when 
freshly  prepared.  It  is  useful  in  studying  the  lamination  of  thick- 
ened cell-walls,  since  it  causes  them  to  swell,  revealing  their  struc- 
ture. It  is  also  used  as  a  test  for  the  presence  of  proteids,  which 
are  disorganized  by  it,  but  after  a  little  while  acquire  a  character- 
istic brick-red  color. 

Glycerin. — This  is  serviceable  for  clearing  sections,  for  preserv- 
ing tissues,  and  for  the  temporary  or  permanent  mounting  of  ob- 
jects, though  for  this  purpose  glycerin  gelatin  is  in  most  cases  to 
be  preferred.  Cell-wall  structures  are  usually  better  seen  in  glyc- 
erin than  in  resinous  mounting  media,  and  starch-grains  are  not 
so  much  obscured  by  it.  A  mixture  of  equal  parts  of  glycerin 


266  LABORATORY    EXERCISES    IN    BOTANY. 

aud  alcohol  is  highly  serviceable  for  the  treatment  of  tissues  which 
have  been  over-hardened  in  alcohol  and  rendered  too  brittle  to 
be  cut  properly  with  the  section  knife.  An  immersion  of  twenty- 
four  hours  in  the  mixture  will,  if  the  specimens  be  not  too  large, 
usually  suffice  to  put  them  in  a  condition  fit  for  sectioning. 

Glycerin  is  also  employed  to  wash  out  the  excess  of  anilin-blue 
in  the  study  of  sieve-plates. 

Ammonio-ferric  Alum. — A  saturated  solution  of  ammonio-ferric 
alum  in  distilled  water  constitutes  a  very  convenient  test  for  taunic 
matters,  since  it  produces  in  the  cells  containing  it  a  bluish-black 
or  a  greenish-black  precipitate,  according  to  the  variety  of  tannin 
present.  It  should  be  remembered,  however,  that  occasionally 
other  substances,  usually  related  to  the  tannins,  may  be  present, 
which  are  capable  of  producing  dark-colored  precipitates  with 
ferric  salts.  Instead  of  this,  one  may  employ  with  equal  advan- 
tage, when  freshly  prepared,  the  ferric-chloride  solution  described 
in  the  Introduction  to  Part  I. 

Fehling's  Solution. — This  is  prepared  as  follows  :  Dissolve  34.64 
grains  of  pure  copper  sulphate  and  200  grains  of  Rochelle  salt  in 
the  smallest  possible  quantity  of  distilled  water.  Also  dissolve  in 
600  cubic  centimetres  of  distilled  water  a  quantitity  of  sodic 
hydrate  sufficient  to  make  a  liquid  having  the  specific  gravity 
of  1.12.  Keep  the  solutions  separate  in  well-stopped  bottles 
until  required  for  use.  When  needed  to  test  for  sugar,  mix  1 
part  of  the  former  with  2  parts  of  the  latter  liquid,  raise  the 
mixture  to  the  boiling-point,  and  dip  the  sections  to  be  tested, 
for  two  or  three  seconds,  in  the  hot  liquid.  If  grape-sugar  be 
present,  the  cell-contents  will  immediately  be  colored  red  by  the 
precipitation  of  the  suboxide  of  copper ;  if,  instead,  cane-sugar 
be  present,  a  bluish  or  greenish  color  will  be  produced  in  the  cells, 
but  at  first  no  red  color.  On  soaking  the  section  in  the  hot  solu- 
tion for  a  longer  time  a  red  precipitate  gradually  appears,  because 
a  part  of  the  cane-sugar  present  is  converted  into  invert-sugar. 
In  performing  this  test  it  is  better  that  the  sections  should  not 
be  very  thin,  both  because  of  the  inconvenience  of  handling  thin 
sections  and  because  of  the  facility  with  which  the  sugars  escape 
from  them  into  the  hot  solution. 

Fehling's  solution  constitutes  one  of  the  best  tests  for  sugar  in 
tissues. 


INTRODUCTION.  267 

Labarraque's  Solution  (Solution  of  Chlorinated  Soda). — This 
and  the  corresponding  potash  solution,  called  Javelle  water,  are 
useful  clearing  and  bleaching  agents  where  it  is  desired  to  study 
the  cell-walls  without  the  interference  of  the  cell -con  tents.  Sec- 
tions placed  in  either  solution  should  be  watched  carefully  lest 
the  destructive  effects  of  the  reagent  extend  to  the  cell-walls.  If 
the  sections  are  to  be  afterward  stained,  they  must  first  be  washed 
thoroughly  to  get  rid  of  the  last  traces  of  the  bleaching  agent. 
The  solutions,  which  are  readily  obtainable  at  most  pharmacies, 
should  be  kept  in  a  dark  place  and  in  tightly-stopped  bottles. 
They  require  also  to  be  frequently  renewed. 

Javelle  Water  (Solution  of  Chlorinated  Potash). — Used  for  the 
same  purposes  as  Labarraque's  Solution  (see  above). 

Chloral-hydrate  Solution. — Used  as  a  clearing  agent.  (See 
Chloral-hydrate  Iodine,  p.  264). 

Diphenylam'm  Solution. — A  good  formula  for  the  preparation 
)f  this  reagent  is  that  of  Strasburger :  Dissolve  0.5  grain  of 
the  crystals  in  10  cubic  centimetres  of  pure  sulphuric  acid.  The 
solution  is  employed  as  a  test  for  nitrates,  tissues  containing  them 
turning  blue  on  applying  the  reagent,  from  the  formation  of 
aniliu-blue.  The  nitrites  show  the  same  reaction,  but  are  very 
seldom  found  in  plants. 

Anilin  or  Anilin  Oil. — This  liquid  is  sometimes  used  as  an 
intermedium  between  water  and  balsam,  to  obviate  the  necessity 
of  complete  anhydration  by  alcohol.  Since  anilin  dissolves  about 
four  per  cent,  of  water,  the  sections  may  immediately  be  trans- 
ferred from  aqueous  liquids  to  anilin,  and  then  from  this  to  bal- 
sam. The  anil  in  may  be  kept  free  from  water  by  placing  solid 
potassium  hydrate  in  the  containing  vessel,  the  alkali  possessing  a 
strong  affinity  for  water  and  being  wholly  insoluble  in  the  auilin. 

Potassium  Bichromate. — A  saturated  solution  of  the  salt  in  dis- 
tilled water  is  often  employed  as  a  test  for  tannic  matters,  most 
tannins  forming  with  it  a  yellowish-brown  or  dark-brown  pre- 
cipitate. Structures  containing  tannin  may  be  placed  en  masse 
in  the  solution  for  twenty-four  hours  or  more,  and  then  be  washed, 
sectioned,  and  examined.  The  masses,  however,  must  not  be  of 
very  large  size,  as  the  solution  penetrates  rather  slowly.  This 
reagent  is  not  wholly  satisfactory  as  a  tannin  test,  since  some  other 
compounds  besides  the  tannins  form  brownish  precipitates  with  it, 


268  LABORATORY    EXERCISES    IN    BOTANY. 

Ill  1  or  2  per  cent,  aqueous  solution  the  bichromate  is  sometimes 
employed  in  vegetable  as  it  is  in  animal  histology,  as  a  hardening 
agent,  though,  on  the  whole,  it  is  much  less  serviceable  than  alcohol. 

Potassium  Ferrocyanide. — A  10  per  cent,  aqueous  solution  has 
been  employed  successfully  in  connection  with  ferric  chloride  in 
staining  proteids  and  in  demonstrating  the  stratification  in  thick- 
ened cell- walls.  For  the  former  purpose,  according  to  Zimmer- 
mann,  the  solution  is  prepared  by  dissolving  10  per  cent,  of  the 
salt  in  a  mixture  of  equal  portions  of  water  and  acetic  acid, 
specific  gravity  1.063.  The  solution  must  be  freshly  prepared, 
as  it  readily  spoils.  In  it  the  sections  are  soaked  for  a  few  hours, 
and  then  washed  in  60  per  cent,  alcohol  until  the  washing  fluid 
no  longer  gives  a  blue  color  with  ferric  chloride ;  they  are  then 
treated  with  a  dilute  solution  of  ferric  chloride,  when,  owing  to 
the  tenacity  with  which  the  proteid  matters  retain  the  ferrocyauide, 
they  will  be  stained  by  the  precipitation  in  them  of  Berlin  blue, 
while  the  cell-walls  will  be  scarcely,  if  at  all,  stained. 

For  the  study  of  the  cell-wall  stratification  the  following  plan 
may  be  pursued  :  Treat  the  sections,  previously  dried,  in  a  10  per 
cent,  solution  of  the  ferrocyanide,  take  up  the  superfluous  liquid 
with  blotting  paper,  and  then  immerse  them  for  a  few  moments 
in  a  dilute  solution  of  ferric  chloride :  Berlin  blue  will  be  precip- 
itated in  the  strata,  and  more  in  those  which  are  capable  of  taking 
up  the  most  water,  hence  the  strata  will  be  seen  more  distinctly. 

Silver  Nitrate. — This  is  sometimes  employed,  in  2  or  3  per  cent, 
solution  in  distilled  water,  for  the  study  of  the  lamination  in 
starch-grains  and  in  thick-walled  cells.  The  structures  are  first 
thoroughly  dried  at  a  temperature  of  about  60°  C.,  and  then 
treated  with  the  solution  for  a  few  hours.  After  draining  off  the 
superfluous  liquid  and  again  drying,  the  structures  are  immersed 
in  a  .75  per  cent,  solution  of  common  salt.  This  precipitates  the 
silver  chloride  in  the  layers,  and  most  abundantly  in  those  which 
take  up  the  solutions  most  copiously,  so  that  after  drying  and  ex- 
posure for  a  short  time  to  strong  light  the  lamina?  or  strata  are 
brought  out  with  great  distinctness.  The  hilum  in  starch -grains 
is  also  rendered  very  conspicuous  by  this  process. 

Tannin  Solution. — A  1  or  2  per  cent,  solution  of  tannin  in  dis- 
tilled water  is  useful  in  connection  with  a  very  dilute  solution  of 
ferric  chloride  or  of  ferric  alum  in  staining  the  walls  of  cells  which 


INTRODUCTION.  269 

have  been  bleached  by  means  of  Labarraque's  solution.  The  pro- 
cess is  as  follows :  Thoroughly  wash  the  sections  after  removing 
them  from  the  bleaching  solution,  then  soak  them  for  a  few 
minutes  in  the  tannin  solution,  then,  after  quickly  draining  oft' 
as  much  as  possible  of  the  liquid,  transfer  them  to  the  solution 
of  ferric  chloride.  Even  very  thin  membranes  may  then  be 
seen  readily,  because  stained  a  deep-black  color.  Tannin  is  also 
used  in  connection  with  osmic  acid  to  stain  crystalloids. 

Sodium  Phosphate. — A  concentrated  solution  of  the  salt  in  dis- 
tilled water  is  employed  in  the  study  of  the  crystalloids  which 
are  contained  in  protein-granules,  as,  for  example,  those  in  the 
endosperm-cells  of  the  castor  bean.  The  reagent  dissolves  all 
the  rest  of  the  grain,  but  leaves  the  crystalloid  unchanged. 

Ctiprammonia. — This  is  prepared  by  adding  to  a  strong  aqueous 
solution  of  copper  sulphate  an  aqueous  solution  of  sodium  hydrate, 
collecting  the  resulting  precipitate  by  allowing  it  to  settle,  and 
then  decanting  the  supernatant  liquid.  The  precipitate  is  then 
dissolved  in  strong  ammonia-water.  This  is  the  only  known  re- 
agent capable  of  dissolving  cellulose  without  producing  chemical 
change  in  it.  The  reagent  should  be  used  in  the  undiluted  form, 
and  it  is  better  when  freshly  prepared.  It  does  not  dissolve  lig- 
nified  cell-walls.  The  dissolved  cellulose  may  be  precipitated 
from  solution  by  adding  water. 

Schulze's  Maceration  Mixture. — This  consists  -  of  strong  nitric 
acid  in  which  chlorate  of  potash  has  been  dissolved ;  it  is  chiefly 
used  for  the  isolation  of  cells.  Sections  are  placed  in  this  mixture 
and  gently  heated  until  gases  are  evolved  and  the  reddish  color 
which  first  appears  in  the  tissues  has  disappeared.  The  contents 
of  the  dish  are  then  immediately  poured  into  a  large  quantity  of 
water  to  stop  further  action.  The  sections  are  now  gently  washed 
and  stained  with  methyl-green.  The  cells  may  easily  be  sepa- 
rated by  teasing  or  by  mounting  them  in  a  drop  of  water  on  a 
slide  and  gently  tapping  the  cover-glass  with  a  needle-point. 

The  sections  should  never  be  transferred  from  alcohol  directly 
to  this  mixture,  but  always  from  water ;  otherwise  too  violent,  or 
even  explosive,  effects  may  be  produced.  It  is  better  also  to  let 
the  sections  stand  for  a  few  minutes  in  the  cold  solution  before 
applying  heat,  and  then  great  care  should  be  observed  to  stop  the 
action  at  just  the  right  point,  otherwise  either  the  middle  lamella 


270  LABORATORY   EXERCISES   IN   BOTANY. 

will  not  be  sufficiently  dissolved  to  permit  of  the  separation  of 
the  cells,  or  the  tissues  will  be  destroyed. 

Since  cutinized  tissues  resist  much  longer  than  any  others  the 
action  of  this  liquid,  it  may  be  employed  as  a  test  for  them. 
On  boiling  in  the  mixture  for  some  time,  however,  the  cells  are 
disintegrated  and  converted  into  oily-looking  drops  of  eerie  acid. 

Operations  with  Schulze's  maceration  mixture  should  be  carried 
on  under  a  fume-hood. 

Phloroglucin  Solution. — This  is  used  in  connection  with  hydro- 
chloric acid  as  a  reagent  for  lignified  tissues,  as  already  explained 
in  the  Introduction  to  Part  I.  It  is,  on  the  whole,  the  best  re- 
agent in  use  for  lignified  membranes. 

Anilin  Chlwide. — A  5  per  cent,  alcoholic  solution  of  this  is 
employed  in  the  same  way  as  phloroglucin,  along  with  hydro- 
chloric acid,  as  a  test  for  lignified  tissues.  It  stains  them  a  deep- 
yellow,  while  cellulose  and  cutinized  tissues  remain  unstained. 

Thymol  Solution. — A  20  per  cent,  alcoholic  solution  is  diluted 
with  distilled  water  until  the  thymol  begins  to  be  precipitated,  and 
an  excess  of  potassium  chlorate  is  then  added.  After  standing  for 
a  few  hours  the  solution  is  filtered,  and  it  is  then  ready  for  use. 
It  is  employed  in  the  same  way  as  the  phloroglucin  reagent,  with 
hydrochloric  acid,  as  a  reagent  for  lignified  cell-walls,  which  it 
colors  blue  or  bluish-green. 

Instead  of  thymol,  a  strong  solution  of  phenol,  prepared  by 
saturating  it  with  potassium  chlorate,  may  be  employed  in  the 
same  way  and  with  similar  results. 

a-Naphthol  Solution. — A  15  per  cent,  alcoholic  solution  is  em- 
ployed in  the  same  way  as  phloroglucin,  along  with  hydrochloric 
acid,  for  the  identification  of  lignified  membranes,  which  :uv 
stained  blue-green  by  the  reagent.  With  sulphuric  acid  the 
naphthol  solution  constitutes  a  test  for  glucose,  levulose,  and 
inulin.  Sections  to  be  tested  are  placed  on  a  slide  and  treated 
first  with  the  naphthol  solution,  and  then  a  few  drops  of  strong 
sulphuric  acid  are  added,  when,  if  either  of  the  carbohydrates 
mentioned  be  present,  a  deep-violet  color  will  soon  appear. 

STAINING  FLUIDS. 

A  very  large  number  of  staining  fluids  have  been  used  in  vege- 
table histology,  but  the  following  are  the  most  important : 


INTRODUCTION.  271 

Grenadier's  Alum  Carmine. — A  2  per  cent,  solution  of  ammonia 
alum  in  distilled  water  is  prepared,  and  to  this  is  added  a  little 
powdered  carmine ;  the  mixture  is  boiled  for  twenty  minutes  so 
as  to  produce  a  deep-red  solution,  and  is  then  cooled,  filtered,  and 
a  small  quantity  of  carbolic  acid  added  to  preserve  it.  It  stains 
cellulose  a  bright-red  color,  lignified  cells  less  readily,  and  cutiuized 
cells  not  at  all.  When  allowed  to  act  for  some  time — say  from 
twelve  to  twenty-four  hours — upon  cells  containing  protoplasm, 
the  latter  is  stained,  and  the  nucleus  more  strongly  than  the  rest. 
The  stain  works  best  on  tissues  which  have  laid  for  some  time  in 
alcohol  and  have  then  been  washed  thoroughly  in  water.  By  a 
judicious  use  of  the  J  per  cent,  solution  of  hydrochloric  acid  in 
70  per  cent,  alcohol  the  stain  may  be  washed  out  of  the  cell-walls 
and  the  protoplasm,  remaining  only  in  the  nucleus.  The  solution 
thus  becomes  a  valuable  nuclear  stain. 

Ammonia  Carmine. — Carmine  is  dissolved  in  strong  ammonia- 
water  until  the  latter  is  saturated.  The  solution  is  then  evap- 
orated over  a  water-bath  to  dryness,  and  the  solid  carminate  of 
ammonia  thus  obtained  is  dissolved  in  distilled  water  in  quantity 
sufficient  to  produce  the  requisite  depth  of  color.  This  is  pref- 
erable to  the  carmine  solution  above  described  for  use  with  methyl- 
blue  in  the  double  staining  of  tissues,  but  is  less  useful  as  a  nuclear 
stain. 

Grenadier's  Hcematoxylin  Solution. — A  saturated  solution  of 
hsematoxyliu  in  absolute  alcohol  is  prepared,  and,  in  another  vessel, 
me  of  ammonia  alum  in  distilled  water.  The  solutions  are  then 
lixed  in  the  proportion  of  2  parts  of  the  former  to  75  of  the 
latter.  The  mixture  is  allowed  to  stand  in  the  light  for  a  week, 

then  filtered,  and  to  every  7  parts  of  it  1  part  each  of  glycerin 
and  methylated  alcohol  are  added.  If,  after  standing  for  a  time, 
a  sediment  is  deposited,  the  mixture  should  again  be  filtered. 

Hsematoxylin  solution  stains  both  lignified  and  cellulose  walls, 
but  not  cutinized  ones.  It  is  also  an  excellent  nuclear  stain.  Old 
solutions  are  to  be  preferred,  and  the  best  results  are  obtained 
when  the  sections  are  soaked  for  some  time  in  very  dilute  solu- 
tions. Alcoholic  sections  should  first  be  washed  thoroughly  in 

iter,  and  it  must  be  borne  in  mind  that  the  stain  is  not  com- 
patible with  acids. 

For  nuclear  stains  the  excess  of  stain  should  be  washed  out  of 


272  LABORATORY    EXERCISES   IN    BOTANY. 

the  cell-walls  by  means  of  the  J  per  cent,  solution  of  hydrochloric 
acid  in  70  per  cent,  alcohol.  To  stop  the  action  of  the  acid  at  tlie 
right  point,  it  is  best  to  replace  the  acid  alcohol  with  some  alcohol 
rendered  slightly  alkaline  by  ammonia- water.  The  sections  may 
then  be  auhydrated  and  mounted  in  balsam. 

Methyl-green  Solution. — Dissolve  enough  methyl-green  in  dis- 
tilled water  to  communicate  to  the  liquid  a  deep-green  color. 
This  solution  stains  lignified  and  cutinized  tissues  more  readily 
than  those  composed  of  pure  cellulose.  It  also  stains  protoplasm 
and  the  nucleus.  The  tissues  take  up  the  stain  more  readily  if 
they  have  previously  been  washed  with  water  slightly  acidulated 
with  nitric  acid. 

Acetic  methyl-green  solution,  which  consists  of  a  1  or  2  per  cent, 
solution  of  glacial  acetic  acid  in  distilled  water  in  which  methyl- 
green  is  dissolved  until  a  clear  blue-green  solution  is  produced,  is 
serviceable  for  fixing  and  staining  the  nucleus,  but  the  color  thus 
obtained  cannot  long  be  preserved. 

Iodine-green  Solution. — This  solution  consists  of  distilled  water 
in  which  iodine-green  is  dissolved  until  the  solution  has  a  deep- 
green  color.  It  stains  lignified  and  cutinized  tissues  green,  but 
cellulose  tissues  only  slightly.  It  stains  proteids,  and  is  use- 
ful for  staining  the  amyloplasts  attached  to  young  starch-grains. 
It  is  much  employed,  along  with  carmine,  fuchsin,  or  eosin,  for 
the  double  staining  of  tissues.  In  the  latter  process  better  results 
are  obtained  by  using  the  stains  successively  than  by  mixing  them. 

Anilin-blue  Solution. — The  solution  in  water  is  sometimes  em- 
ployed, along  with  aniliu-water  safranin,  to  produce  a  double 
stain  in  tissues,  the  safranin  going  more  to  the  liguified  and 
cutinized  tissues,  and  the  blue  to  the  cellulose  tissues.  Auiliu- 
blue  is  useful  in  staining  the  callose  of  sieve-tubes.  For  this  pur- 
pose it  is  best  used  very  dilute,  so  that  other  structures  will  not 
be  stained  strongly  by  it.  In  case  of  over-stain,  glycerin  may  be 
used  to  remove  the  excess,  since  this  substance  gradually  removes 
the  color  from  other  structures,  but  leaves  it  in  the  sieve-plates. 

Eosin  Solution. — A  strong  aqueous  or  alcoholic  solution  is  par- 
ticularly useful  in  the  study  of  sieve-tubes,  since  it  stains  the  thin 
albuminous  contents  of  these  tubes  a  deeper  red  than  the  rest  of 
the  structure. 

Dissolved  in  oil  of  cloves,  eosin  is  used  for  clearing  and  at  the 


INTRODUCTION.  273 

same  time  staining  sections  that  have  already  been  treated  with 
anilin-water  gentian-violet  or  iodine-green  and  afterward  anhy- 
drated  with  absolute  alcohol.  A  fine  double  stain  is  thus  produced. 
The  violet  or  green  remains  in  the  lignified  and  cutinized  tissues, 
while  the  cellulose  walls  are  stained  red  by  the  eosin. 

Fuchsin  Solution. — A  solution  of  fuchsin  in  water  may  be  em- 
ployed for  staining  lignified  cell- walls,  which  hold  the  color  more 
tenaciously  than  do  uulignified  ones,  so  that  by  washing  the  sec- 
tions which  have  been  stained  in  fuchsin  with  a  solution  consist- 
ing of  1  part  of  a  saturated  solution  of  picric  acid  in  alcohol  and 
2  parts  of  distilled  water  the  fuchsin  is  wholly  removed  from  the 
unlignified  cell- walls,  while  the  lignified  ones  remain  beautifully 
stained.  The  sections  thus  prepared  may  immediately  be  anhy- 
drated  and  mounted  In  balsam,  or  they  may  first  be  double-stained 
by  the  use  of  anilin-blue. 

Because  fuchsin  also  stains  cellulose  tissues,  it  may  be  used  with 
iodine-green  or  with  methyl-green  to  produce  double  stains  in 
which  the  fuchsin  and  the  green  go  to  the  lignified  and  cutinized 
tissues,  producing,  in  successful  stains,  a  bluish-purple  color,  while 
the  cellulose  tissues  will  be  colored  by  the  fuchsin  only.  The 
most  successful  stains  by  this  method  are  produced  by  using  the 
greens  first,  washing  the  specimens,  and  then  staining  with  the 
fuchsin. 

Safranin  Solution. — Aniliu-water  safranin  is  the  best  prepara- 
tion for  most  purposes.  It  consists  of  equal  parts  by  volume  of 
aniliu-water  (prepared  by  saturating  distilled  water  with  aniliu) 
and  a  concentrated  alcoholic  solution  of  safranin.  When  sec- 
tions of  stems,  roots,  etc.  are  immersed  for  a  time  in  this  solution 
and  then  washed  with  70  per  cent,  alcohol  rendered  slightly  acid 
with  hydrochloric  acid,  the  color  is  removed  from  the  cellulose 
tissues,  and  if  the  process  be  stopped  at  the  right  point  the  cutin- 
ized and  lignified  tissues  alone  remain  stained,  and  these  of  some- 
what different  colors.  Safranin  is  a  most  successful  nuclear  stain 
if  the  sections  be  allowed  to  soak  in  it  for  a  few  hours  and  the 
excess  of  stain  be  washed  out  carefully  with  acid  alcohol. 

Gentian-violet  Solution. — An  excellent  preparation  is  a  mixture 
composed,  by  weight,  of  anilin  3  parts,  gentian-violet  1  part,  alco- 
hol 15  parts,  and  distilled  water  100  parts.  Since,  by  means  of 
alcohol,  the  solution  washes  out  of  cellulose  tissues  more  readily 

18 


274  LABORATORY    EXERCISES    IN    BOTANY. 

than  from  lignified  and  cutinized  ones,  it  may  be  used  to  differ- 
entiate these  tissues.  If,  after  anhydrating  the  washed  specimens, 
they  be  passed  through  oil  of  cloves  in  which  eosiu  has  been 
dissolved,  beautiful  double  stains  will  be  obtained. 

By  means  of  Gram's  method  most  beautiful  and  instructive 
nuclear  double  stains  are  produced.  The  method  is  as  follows : 
The  sections  are  first  soaked  for  about  half  an  hour  in  the  violet 
solution,  and  are  then  washed  first  with  alcohol,  then  in  a  solution 
of  potassium-iodide  iodine  (consisting  of  iodine  1  part,  potassium 
iodide  2  parts,  and  water  300  parts),  then  again  in  alcohol  until 
nearly  all  the  color  has  been  removed  from  the  cell-walls ;  the 
sections  are  then  passed  through  absolute  alcohol  and  into  eosin 
oil  of  cloves,  and  then,  after  a  few  minutes,  they  may  be  mounted 
in  balsam.  The  chromatic  nuclear  figures  will  be  stained  violet, 
and  the  rest  of  the  nucleus  red. 

Another  solution  of  gentian-violet,  particularly  good  for  nuclear 
stains,  consists  of  gentian-violet  dissolved  in  1  per  cent,  solution 
of  acetic  acid  in  distilled  water  until  the  liquid  has  acquired  a 
deep-violet  color. 

Corallin  Solution. — This  useful  stain  is  prepared  as  follows: 
Dissolve  3  grains  of  sodium  carbonate  in  2  ounces  of  distilled 
water,  and  in  the  solution  thus  obtained  dissolve  10  grains  of 
coralliu,  and  filter.  In  order  to  preserve  the  liquid,  place  in  the 
bottle  containing  it  a  few  grains  of  camphor.  Corallin  thus  pre- 
pared stains  cellulose  and  lignified  membranes  different  shades  of 
red,  sieve-callose  a  very  brilliant  red,  and  starch -grains  red.  The 
colors,  however,  are  not  permanent. 

Picric-nigrosin  Solution. — A  good  preparation  is  the  following : 
To  a  saturated  solution  of  picric  acid  in  distilled  water  is  added 
enough  of  a  strong  aqueous  solution  of  nigrosin  to  give  to  the 
liquid  a  deep  olive-green  color.  This  solution  fixes  and  at  the 
same  time  stains  the  nucleus,  and  for  this  purpose  is  especially 
useful  in  the  study  of  the  filamentous  algae.  Specimens  usually 
require  to  be  soaked  in  the  solution  for  fully  twenty-four  hours 
in  order  to  obtain  satisfactory  results. 

Picric-nigrosin  solution  is  also  serviceable  as  a  double  stain  for 
sections  of  roots,  stems,  etc.,  the  nigrosin  going  to  the  cellulose 
and  the  picric  acid  to  the  lignified  tissues.  The  preparations  arc 
either  in  balsam  or  in  glycerin  jelly. 


INTRODUCTION.  275 

Oyanin  Solution. — A  solution  of  cyanin  in  equal  parts  of  alco- 
hol and  distilled  water  is  employed  for  the  study  of  fats,  which 
are  colored  a  beautiful  blue  after  soaking  for  half  an  hour  or  more 
in  the  solution.  Glycerin  or  a  strong  solution  of  potassium  hy- 
drate may  be  employed  for  washing  out  the  superfluous  stain. 
The  color  is  not  permanent. 

Alcannin  Solution. — This  stain  is  prepared  by  adding  to  the 
strong  solution  in  absolute  alcohol  distilled  water  until  a  pre- 
cipitate begins  to  be  formed,  and  then  filtering.  It  is  used  for 
the  detection  of  fats,  resins,  and  volatile  oils,  which  after  a  little 
time  it  colors  a  deep-red. 

The  same  solution  may  be  employed  for  the  identification  of 
cutinized  and  suberized  tissues,  which  after  a  few  hours  are  col- 
ored decidedly  by  it*  though  not  of  so  deep  a  red  as  are  oily  or 
resinous  substances. 

Great  care  should  be  exercised  in  the  selection  of  the  colors  for 
staining,  especially  the  coal-tar  colors.  Many  of  the  safranins  in 
the  market,  for  example,  are  worthless  for  the  purposes  of  vege- 
table histology.  Only  those  colors  should  be  purchased  which 
are  certified  to  by  reliable  dealers  as  suitable  for  microscopic  use. 

PERMANENT  MOUNTING  OR  ENCLOSING  MEDIA. 

The  most  valuable  are  the  following : 

Canada  Balsam,  or  Balsam  of  Fir. — This  should  be  nearly 
colorless  and  entirely  free  from  solid  impurities.  It  may  be  kept 
in  a  capped  bottle ;  but  a  better  way  is  to  obtain  it  in  collapsible 
tubes  of  tin,  which  are  now  commonly  sold  by  dealers  in  micro- 
scopical supplies.  The  ordinary  or  natural  balsam,  which  con- 
sists of  resin  in  solution  in  oil  of  turpentine,  may  be  employed, 
or,  as  the  writer  prefers,  the  solution  of  the  hardened  resin  in 
xylol. 

Balsam  mounts,  though  somewhat  troublesome  to  make,  are 
very  durable  and  satisfactory. 

Glycerin  gelatin  of  good  quality  may  be  prepared  as  follows : 
Soak  for  an  hour  or  more  1  ounce  of  the  best  French  or  German 
gelatin  in  3  ounces  of  distilled  water,  and  then  raise  the  tempera- 
ture nearly,  but  not  quite,  to  the  boiling-point,  until  the  gelatin 
is  completely  dissolved ;  add  4  ounces  of  pure  glycerin  and  as 
many  drops  of  95  per  cent,  carbolic  acid,  very  gently  stirring  the 


276  LABORATORY    EXERCISES    IN    BOTANY. 

mixture  with  a  glass  rod,  so  as  to  mix  thoroughly  and  at  the  same 
time  to  avoid  air-bubbles,  aud  then  allow  the  mixture  to  cool.  It 
soon  sets  and  forms  a  clear,  transparent  jelly.  If  the  gelatin  used 
is  of  the  finest  quality  and  perfectly  free  from  superficial  dust 
(which  may  be  ensured  by  rinsing  rapidly  in  cold  distilled  water 
before  using),  filtering  or  straining  will  be  unnecessary. 

Carmine-stained  preparations  are  uu suited  to  this  medium,  as 
the  carmine  is  soluble  in  it.  The  same  is  true  of  several  of  the 
anilin  stains  (see  Table).  Haematoxylin-stained  specimens  keep 
well  in  glycerin  gelatin,  providing  it  contains  no  trace  of  acid. 

Glycerin  alone  is  often  employed  as  a  mounting  medium,  but 
is  troublesome  on  account  of  the  difficulty  of  enclosing  it.  For 
nearly  all  purposes  glycerin  gelatin  answers  as  well,  and  it  is  far 
more  convenient. 

PROCESSES  OF  MOUNTING. 

The  process  of  enclosing  in  balsam  may  be  outlined  briefly  as 
follows:  First,  the  sections,  if  they  have  been  stained  in  any 
aqueous  medium,  must  be  anhydrated,  and  this,  especially  if  they 
be  delicate,  must  be  done  gradually  by  transferring  them  first  to 
weak  alcohol,  then  to  stronger,  and  so  on  through  solutions  of 
gradually  increasing  strength  to  absolute  or  at  least  98  per  cent, 
alcohol.  The  sections  are  then  usually  passed  through  a  clearing 
medium  such  as  oil  of  turpentine,  oil  of  cloves,  xylol,  or  oil  of 
bergarnot,  and  are  then  placed  on  the  centre  of  the  slide  and  im- 
mediately covered  with  a  drop  of  balsam,  on  which  is  placed  the 
cover-glass,  care  being  taken  to  put  it  on  in  such  a  manner  as  not 
to  entrap  air-bubbles  and  to  get  it  in  the  centre  of  the  slide.  If 
just  the  right  quantity  of  balsam  has  been  used,  and  none  has 
oozed  out  around  the  edges  of  the  cover-glass,  nothing  further  is 
really  necessary  except  to  let  the  balsam  harden  ;  but  some  prefer 
to  "finish'7  the  slides,  for  appearance'  sake,  by  ringing  them. 
This  is  done  by  running  a  circle  of  cement  around  the  edge  of 
the  cover-glass  by  means  of  a  fine  pointed  brush  and  a  turn-table. 
Of  course,  no  colored  or  opaque  cement  that  is  soluble  in  balsam 
should  be  employed  for  this  purpose,  because  sooner  or  later  the 
cement  would  run  under  the  cover-glass  and  spoil  the  specimen. 

In  cases  where,  for  some  reason,  it  is  not  desirable  to  pass  the 
sections  through  alcohol,  and  yet  it  is  of  importance  to  mount  them 


INTRODUCTION.  277 

in  balsam,  anhydration  may  be  avoided  by  transferring  them  from 
the  aqueous  medium  gradually  to  a  concentrated  solution  of  car- 
bolic acid,  and  then  immediately  to  balsam. 

Instead  of  carbolic  acid,  aniliu  may  be  employed  in  the  same 
way. 

The  process  of  mounting  in  glycerin  gelatin  is  quite  simple,  but 
here  also  the  effects  of  osmosis  must  be  borne  in  mind.  If  the 
specimens  are  delicate,  it  will  not  do  to  transfer  them  at  once 
from  water  or  dilute  alcohol  to  the  enclosing  medium.  They 
must  gradually  be  brought  through  weak  into  strong  glycerin, 
and  then  be  transferred  to  the  glycerin  gelatin.  A  very  good 
way  to  accomplish  the  gradual  transition  is  first  to  place  the  sec- 
tions in  10  or  15  per  cent,  glycerin,  and  let  this  solution  gradually 
concentrate  by  evaporation  in  a  dry  place  protected  from  dust. 
The  sections  may  then  be  transferred  directly  to  the  slide,  the 
superfluous  glycerin  be  taken  up  by  blotting-paper,  and  a  drop 
of  the  liquefied  gelatin  be  placed  upon  them.  The  gelatin  may 
readily  be  liquefied  as  occasion  requires  by  placing  the  containing 
vessel  in  a  dish  partly  filled  with  water  and  gradually  applying 
heat. 

It  is  advisable  to  use  just  enough  of  the  medium  to  fill  the 
space  between  the  cover-glass  and  the  slide.  After  the  gelatin 
has  set,  it  is  desirable  to  protect  the  mount  from  injury  by  run- 
ning a  ring  of  some  resinous  cement — balsam,  for  example — 
around  the  edge  of  the  cover-glass.  After  a  long  time  the  bal- 
sam is  liable  to  crack.  To  prevent  this  the  ring  of  balsam,  after 
a  few  days,  may  be  covered  with  one  of  gold-size.  The  mount 
is  then  almost  as  permanent  as  one  in  balsam. 

DRAWING  MICROSCOPIC  OBJECTS. 

What  was  said  in  the  General  Introduction  about  the  import- 
ance of  drawing  is  here  repeated  with  emphasis.  Every  student 
who  undertakes  the  work  of  the  microscopical  laboratory  should 
by  all  means  practise  it.  For  this  purpose  he  should,  at  the  out- 
set, provide  himself  with  a  suitable  pencil  and  a  drawing-book. 
Of  course,  drawings  made  by  the  aid  of  a  good  camera  lucida, 
such  as  that  described  in  the  Appendix  to  Part  II.,  College  Bot- 
any, are  likely  to  be  somewhat  more  accurate  than  those  made 
without  its  use,  but  the  advantages  of  such  an  instrument  are 


278  LABORATORY    EXERCISES    IN    BOTANY. 

likely  to  be  over-estimated.  In  fact,  dependence  upon  it  tends 
to  foster  slavish  copying,  to  the  detriment  not  only  of  artistic 
skill,  but  to  that  of  the  observing  faculties  of  the  student.  The 
student's  first  efforts  at  drawing  should  be  undertaken  without 
the  aid  of  the  camera,  and  he  should  begin  with  simple  struc- 
tures, such  as  single  cells,  starch-grains,  etc.,  and  after  ho  has 
acquired  some  degree  of  skill  proceed  to  more  complex  ones. 
The  apparent  dimensions  of  the  object  may  readily  be  trans- 
ferred to  paper,  either  by  means  of  a  pair  of  dividers  or  by 
means  of  a  graduated  scale  as  suggested  on  page  254. 

In  using  the  camera  lucida  it  is  of  importance  that  the  draw- 
ing-paper and  the  field  of  the  microscope  should  be  nearly  equally 
illuminated,  otherwise  the  pencil-point  and  the  object  to  be  delin- 
eated cannot  be  seen  with  equal  distinctness,  and  the  outlines 
of  the  structure,  therefore,  cannot  be  followed  with  accuracy. 
The  outlines  should  be  traced  with  a  fine-pointed,  hard  pencil 
such  as  Faber's  or  Hardtmuth's  HHH.  The  tracing  should  be 
made  on  smooth-finished  white  paper  or  cardboard.  The  camera 
will  seldom  be  used  except  to  draw  outlines  and  locate  important 
points ;  to  fill  in  the  minute  details  by  means  of  it  is  usually 
impracticable. 

Drawings  designed  merely  as  a  record  of  observations  or  for 
the  wood-engraver  may  be  left  in  lead-pencil,  but  those  that  are 
to  be  reproduced  by  photographic  process  should  be  drawn  in  the 
blackest  of  black  ink. 

GENERAL  DIRECTIONS  FOR  WORK. 

(1)  The  student  should  at  the  very  outset  thoroughly  acquaint 
himself  with  the  mechanism  of  the  microscope  and  the  accessory 
apparatus  with  which  he  has  to  work,  that  he  may  use  them  intel- 
ligently. 

(2)  He  should  observe  great  care  in  the  removal  and  putting  on 
of  objectives,  so  as  not  to  drop  them.     Eye-pieces  and  micrometer 
should  also  be  handled  with  especial  care. 

(3)  He  should  observe  care  in  focusing,  particularly  with  high 
powers,  so  as  not  to  run  the  objective  down  against  the  slide,  and 
thus  endanger  breaking  either  the  cover-glass  or  the  objective. 
He  should  take  care  also  that  the  object  is  in  accurate  focus, 
otherwise  it  cannot  be  seen  distinctly. 


INTRODUCTION.  279 

(4)  He  should  give  due  attention  to   the  adjustment  of  the 
reflecting  mirror,  so  as  to  secure  the  most  perfect  illumination 
of  the  object.     Much  of  his  success  in  seeing  will  depend  upon 
the  care  with  which  this  is  done. 

(5)  He  should  bear  in  mind  that  many  of  the  reagents  em- 
ployed are  corrosive,  and  be  correspondingly  careful  in  the  use 
of  them.     Some  of  the  acids  are  volatile,  which  is  a  reason  for 
keeping  the  containing  bottles  stopped  when  not  in  actual  use; 
all  the  acids  and  iodine  will  act  on  brass-work ;  potassium  hy- 
drate will  corrode  glass ;  Schulze's  maceration  fluid  evolves  very 
corrosive  fumes,  which  should  not  be  permitted  to  escape  into  the 
room ;  and  even  alcohol  and  alcoholic  solutions  will  remove  the 
lacquer  from  the  brass-work  of  the  microscope. 

(6)  Nearly  all  objects  to  be  examined  will  be  studied  as  trans- 
parent objects — that  is,  they  will  be  studied  by  transmitted  light — 
and  they  will  therefore  be  mounted  in  liquid  of  some  kind,  and 
should  always  be  covered  with  a  cover-glass,  not  only  to  avoid 
the  distortion  of  the  image  which  a  curved  or  uneven  liquid  sur- 
face inevitably  produces,  but  to  protect  the  objective.      Before 
placing  the  mounted   object  on  the  stand  all   liquid  that  oozes 
from  under  the  edges  of  the  cover-glass  should  be  wiped  away. 

(7)  Cleanliness  should  characterize  all  the  work  of  the  micro- 
scopical laboratory.  All  apparatus,  slides,  cover-glasses,  etc.  should 
be  kept  scrupulously  free  from  dirt.     The  glasses  of  the  objectives 
and  the  eye-pieces  should  never  be  touched  with  the  fingers,  for 
that   would   soil   them   and    impair  their   optical    performance. 
Whenever  they  need  cleaning,  which  should  not  be  often,  the 
glasses  should  be  breathed  upon  and  be  wiped  gently  either  with 
a  piece  of  perfectly  clean  and  soft  linen  cloth  or  with  a  piece  of 
the  thin,  soft  paper  that  is  sold  at  dental  supply  stores  under  the 
name  of  "  Japanese  filter-paper."     A  convenient  way  is  to  keep 
always  at  hand,  in  a  place  secure  from  dust,  a  quantity  of  this 
paper  cut  into  suitable  sizes.     It  is  useful  also  for  cleaning  cover- 
glasses,  slides,  etc.     If  a  fresh  piece  be  used  each  time,  there  will 
be  little  danger  that  the  glass  of  an  objective  or  an  eye-piece  will 
be  scratched  or  marred  or  its  polish  dimmed.    All  bottles  contain- 
ing reagents  and  stains  should  be  kept  stopped  to  prevent  evap- 
oration and  the  entrance  of  dust  when  not  in  actual  use;  the  glass 
tubes  used  in  applying  the  tests  should  always  be  returned  imme- 


280  LABORATORY    EXERCISES   IN    BOTANY. 

diately  to  the  proper  bottles.     Care  ought  also  to  be  exercised  not 
to  put  the  caps  on  the  wrong  bottles. 

(8)  It  is  very  important  that  the  razor  or  section   knife  for 
cutting  sections  be  always  keen-edged,  and  the  student  should 
provide  himself  with  the  necessary  appliances  for  sharpening. 
For  most  purposes  sections  require  to  be  cut  quite  thin.     The 
knife  should  be  given  an  oblique  or  sliding  motion  in  cutting,  and 
should  be  pushed  rather  than  drawn  through  the  object.     The 
motion  should  be  steady  and  even,  and  never  a  to-and-fro  or  saw- 
ing motion.    The  forefinger  of  the  hand  holding  the  object  should 
be  extended  slightly,  so  as  to  form  a  rest  for  the  razor-blade  as 
well  as  to  assist  in  starting  the  section  of  the  right  thickness. 
Quite  hard  tissues  may  be  cut  successfully  if  only  very  thin  sec- 
tions of  them  are  attempted,  but  if  the  knife-edge  is  allowed  to 
run  deep  it  is  liable  to  be  notched.     Portions  of  thin  structures, 
such  as  leaves,  petals,  and  stamens,  may  readily  be  sectioned  by 
placing  them  between  pieces  of  elder  or  sunflower  pith  and  cut- 
ting through  pith  and  all.     In  case  the  tissue  to  be  cut  is  quite 
hard,  cork  may  often  advantageously  be  substituted  for  the  pith. 
Longitudinal  sections  of  such  small  objects  as  ovules  may  often 
successfully  be  made  by  putting  them  between  flat  pieces  of  cork 
or  pith  and  running  the   knife-blade  vertically  through  them 
between  the  pieces  of  supporting  material. 

The  knife  should  always  be  cleaned  carefully  after  using  it,  and 
pieces  of  tissue  should  never  be  allowed  to  dry  upon  it,  otherwise 
its  surface  will  soon  become  tarnished  by  the  acids  and  tannins  in 
the  tissues,  and  sections  will  not  so  readily  slide  up  on  the  blade, 
but  will  fold  or  crumple. 

In  most  instances  it  is  best  in  cutting  to  keep  the  knife-blade 
wet  with  alcohol  or  with  a  mixture  of  equal  parts  of  alcohol  and 
glycerin.  Sections  of  fresh  tissues  or  of  those  that  have  been 
kept  in  any  of  the  preservative  fluids  should,  immediately  after 
cutting,  be  transferred — best  by  means  of  a  camePs-hair  brush — 
to  liquid,  otherwise  air  will  get  into  the  cells  and  seriously  impair 
the  value  of  the  section  for  study. 

(9)  The  student  should,  in  all  his  work  with  the  microscope, 
proceed  understandiogly,  endeavoring  to  know  the   reason   for 
every  test  he  is  directed  to  apply,  and  carefully  interpreting  the 
results  of  each  test. 


INTRODUCTION.  281 

(10)  It  is  excellent  practice  for  the  student  to  keep  an  accu- 
rate record,  both  in  writing  and  by  means  of  drawings,  of  the 
work  done  and  the  facts  observed  in  the  laboratory. 

The  following  table  gives  a  bird's-eye  view  of  the  different  re- 
agents and  stains,  their  composition,  and  their  most  important  uses. 
The  student  will  find  it  convenient  for  reference. 


TAIU.K   OF    KF\< 


Acid,  chromic 


riuic. 

Acid. 
hydrochloric. 

"  "Swells 

Acid,  nitric.         »^£f 
withJO^ ! 


aiui 
defines 


Clears 

- 


1C 

With 


tion. 


Swells. 


Aeid,08mic, 


nd.  picric. 


huric. 


plasiu. 

Ren- 

ders  dis- 
tinct 
and 
slowly 


solves. 


50«  alcohol). 


AlnM 


Alum,  atnnuv 


Decol- 


DB- 


out 

chloro- 
phyll. 


Colors 


t.n>. 
teids 


dis- 


verv 
slowly. 


Stains      Stains 
slowly     bricht 


Hani- 


"^  dr~ 

ton  oils  nucleus     . 


Fixes 
proto- 


Alum  ^.iriiunc. 


Anilin-blue. 


Anilin  chloride 


red. 

HK 


AND  STAINS. 


Middle 

lamella. 

Mounting 
medium. 

Nitrates. 

Nucleus. 

03 

d 
| 

Starch. 

1 

02 

Swelling. 

Tannin. 

Form  in  which 
used. 

and 

defines. 

It 

defines. 

With 
alcohol 
fixes. 

Solution  in 
water  or  alco- 
hol. 

Green 
or 
blue- 
11 

Mostly  strong 
solution  in 
water. 

S 

solves 
slowly. 

25$ 
dis- 
solves 
readilv. 

l-i  fixes 
and 
stains 
brown. 

•£. 

Solution  in 
water. 

l> 
defines. 

In  water  or  with 

methyl  -green. 

Yellow 
with 
ammo- 
nia. 



Disor- 
ganizes. 
Yellow" 
with 

:i  in  nio- 
nia. 

Swells. 



Usually  strong. 

Dis- 
solves. 

Usually  strong. 



Fixes. 

Fixes. 



Stains 
bluish 
or 
brown- 
ish. 

In  |#  or  1#  aque- 
ous solution. 

Stains 

j  yellow. 

s,,,,, 

solves 
i  slowly. 



Fixes. 

Fixes. 

In  saturated 
aqueous  or  al- 
coholic solu- 
tion. 

Strong 
dis- 
solves 
slowly. 

Dis- 
solves. 

The    pure    acid 
or  mixed  with 
one-third 
water. 





Mostly  dilute  in 

alcohol. 



Fixes. 

Stains 
bright 
red. 

Sol.  in  alcohol 
diluted  with 
water  to  50$. 

Fixes. 

Dis- 
solves. 

Absolute  for 
anhydrating. 

Stains 
nucleus 
red. 

Green- 
ish- 
)lack  or 
bluish- 
black 
precip- 
itate. 

Concentrated 
solution  in 
water. 

Balsam. 

Stains 
red. 

See  formula. 

3alsam  . 

Stains 
red. 

Stains 
red. 

Stains 
blue. 



See  formula. 

Colors 
1  yellow. 

lialsum 
and 
glyc- 
erin. 





Aqueous  solu- 
tion. 

5$  alcoholic  sol. 
first,  then 
strong  HC1. 

T.U;: 


' 


Mue 


I1 

'_ 
\ 

| 

j 

i 

1 

I 

2 

I 

= 

*S 

1,-,  ,1 

dratiuK  in 

tad* 

UaMatfd 

-w.-lh 

Strong 
•olui 

t«d. 

itti. 

Sofiitioi 

I'.lm- 

cc.   of 

IIZHI.. 

l:.-.|. 

for   M 

idhnM 

ia 

j,i,«ii,. 

!.:,.,. 

with 

Ithtiw. 

He«  formula. 

•ad 

J'.,.i 

AIJIMMHW.OIU. 

Mm 

Vj.,l.-l. 

I0l«( 

Man.lv   a, 

',:;:* 

See  formula. 

KreIE 

and 
to 
itoOQ 

lUiDi 

See  formula. 

HaNiiin 

l'i'»\»  ii 

J',r</\*ii. 

, 

KM 
»w«lk 
Dddte- 

See  formula. 

De- 

*m 

1,,- 
*tr<>\  » 

t  wall?  .iii.,i.-i. 

i..- 

I'.r 

Fixe*. 

fUtf, 

aqueotui  «olu- 

TABLE  OF  KEAGKNTS 


1 

>» 

Amyloplasts. 

I 

1 

Chloroplasts. 

1  Clearing. 

Crystalloids. 

Cutin  or 
Suberin. 

I 

W 

q 
'* 

£ 

Hardening. 

Methyl-green. 

Green. 



Methyl-green 
(acetic). 

' 

Green. 

Millon's 
reagent. 

Swells. 





a-naphthol  (15j« 
sol.). 



Phloroglucin 
reagent. 

Picric  nigrosin. 

Green- 
ish. 

Proto- 
plasm 
and 

nuch'Uh 

Potassium 
bichromate. 

$  °r  2* 
solu- 
tion. 

Potassium 
ferrocyanide. 

Blue 
with 
sol.  of 
ferric 
chlor. 

Potassium 
hydrate. 

Swells 

Dis- 
solves 
proteid 
and 
starch 

Strong 
and  hot 
Yellow 

Sapon- 
ifies. 
Fatty 
acids 
crvstal- 
1'ize. 

Safranin. 

! 

Red 
easily 
washe< 
out. 

De- 
stroys 
when 
hot 

rathe 
rapidly 

Deep 
red. 

Schulze's  mace 

cation  mix- 
ture. 

De- 
stroys 

slowly. 
Before 
KHO 

yellow. 



nitrate 

Sodium  phos- 
phate. 

Insol- 
uble in 

Tannin. 

Kla.-k 

with 

IVrru 
chlor 

Brow  i 
before 

usmic 
acid. 

Thymol. 

AND  STAINS  (CONTINUED). 


a 
1 

3 

dj 

03  "QJ 
VS 

3£ 

§* 

11 
5  2 

^ 

Nitrates. 

Nucleus. 

Proteids. 

4 
q 

Starch. 

8, 
£ 

Swelling. 

Tannin. 

Form  in  which 
used. 

Green. 

Balsam 
and 
glyc- 
erin. 

Green. 

Aqueous  solu- 
tion. 

Green. 

Not  per- 
manent 
in  bal- 
sain  or 
glyc- 
erin. 

Green. 

Green. 

Used  as  nuclear 
stain. 

Swells. 

Red- 
dens 
and 
disor- 
ganizes. 

Swells. 

Solution  must 
often  be  re- 
newed. 

With 
HC1 
blue- 
green. 

Violet 
with 
H2S04. 

Red 
with 
HC1. 

5<jt>  alcoholic  so- 
lution and 
HC1. 

Yellow. 

Balsam 
and 
glyc- 
erin. 

Blue- 
green. 

See  formula. 

Brown- 
ish 
precipi- 
tate. 

For  tannin 
strong  solu- 
tion in  water. 

Blue 
with 
sol.  of 
ferric 
chlor. 

Used  for  study 
of  cell-walls. 

Strong 
and  hot. 
Dis- 
solves. 

De- 
stroys. 

De- 
stroys. 

Strong. 
Yellow- 
ish or 
brown- 
ish. 

In  aqueous  solu- 
tion mostly. 

?e1" 

Balsam. 

Red. 

Red. 

See  formula. 

De- 

stroys 
when 
hot 
rather 
rapidly. 

Dis- 
solves 
readily. 

HNO3  with 
KC103  in 

solution. 

Balsam. 

Shows 
strata 
in. 

Used  in  5%  aque- 
ous solution 
for    study   of 
starch. 

Dis- 
solves, 
except 
crystal- 
loids. 

Strong  aqueous 
solution. 

Black 
with 
1  ferric 
chlor. 

With  Fe2Cl6  for 
study  of  thin 
membranes. 

Green 
or  blue- 
green 
with 
HC1. 

Red 
before 
H2S04. 

See  formula. 

EXERCISE  I. 

THE  TYPICAL  VEGETABLE  CELL. 

SELECTIONS  for  study  may  be  made  from  among  the  follow- 
ing objects :  the  colorless  epidermis  of  one  oT  the  fleshy  scales 
of  an  Onion,  Lily,  Hyacinth,  or  Amaryllis  bulb ;  the  leaves  of 
some  of  the  mosses  and  liverworts,  as,  for  example,  those  of 
Bryum  roseum,  Schreb.,  Mnium  cuspidatum,  Hedw.,  Jubula 
Hutchinsise,  Dumort.,  and  Jungermannia  Schraderi,  Martins;  or 
the  filaments  of  some  of  the  filamentous  algae,  as  Cladophora 
glomerata,  Kvizing,  (Edogonium  princeps,  Wittr.,  Spirogyra 
crassa,  Kvizing,  or  Zyguema  insigne,  Kutzing. 

For  the  present  study  selection  is  made  of  the  epidermis  of 
one  of  the  fleshy  scales  of  the  Onion  (Allium  Cepa,  JL),  pref- 
erably that  from  the  dorsal  or  convex  surface  of  the  scale. 

(1)  With  the  razor  cut  through  the  epidermis,  but  as  little  as 
possible  into  the  sublying  tissues,  and,  seizing  the  epidermis  be- 
tween the  thumb  and  the  razor-edge,  strip  it  off  and  immediately 
transfer  it  to  a  slide  previously  wet  with  a  drop  of  water; 
flatten  it  out  with  a  camePs-hair  brush,  by  means  of  the  scis- 
sors or  a  knife-blade  trim  away  those  portions  of  it  which  have 
some  of  the  sublyiug  tissue  attached,  and  cover  the  remainder 
with  a  cover-glass.  In  doing  this  be  sure  there  is  enough  water  on 
the  specimen  completely  to  fill  the  space  between  the  cover-glass 
and  the  slide.  The  cover-glass — which,  to  prevent  soiling,  should 
be  handled  with  the  pincettes,  and  not  with  the  fingers — should 
be  brought  down  on  the  specimen  one  edge  first  or  at  a  consider- 
able angle  with  the  slide,  and  then  should  gradually  be  pressed 
down  into  position.  This  is  for  the  purpose  of  driving  out  the 
air.  Air-bubbles  seriously  interfere  with  the  view  of  the  struc- 
ture, and  in  all  mounting,  whether  temporary  or  permanent, 
must  carefully  be  avoided.  Care  should  be  taken  also  to  place 
the  object  and  the  cover-glass  as  near  the  centre  of  the  slide  as 
possible. 

283 


284  LABORATORY    EXERCISES    IN    BOTANY. 

*  t 

(2)  The  slide  is  now  placed  on  the  stage  of  the  microscope, 
with   the  object  over  the  centre  of  the  stage  aperture,  and  is 
brought  into  the  focus  of  a  low-power — say  the  two-third-inch 
— objective.     Where  a  doubly  or  triple  nose-piece  is  employed 
it  is  best  always  to  focus  upon  the  object  with  the  low  power, 
and    then    afterward,   if  necessary,    with   a   higher   one,  as   the 
objective  and  the  nose-piece  are  so  arranged,  or  should  be,  that 
when   the  object  is   in  the  focus  of  the  low  power,  by  simply 
rotating   the   nose-piece  and  bringing   the  high-power  objective 
into  position  the  Object  will  be  very  nearly  in  the  focus  of  this 
also.      This    makes    focusing   with    the   high    power   easy,    and 
avoids  the  danger  of  running  the  objective  down  on  the  cover- 
glass.     In  focusing  with  the  low  power  it  is  also  good  practice, 
before  looking  into  the  tube,  to  rack  the  objective  down  to  within 
about  a  quarter  of  an  inch  of  the  object,  and  then,  while  looking 
through  the  tube,  rack  it  up  again  until  the  object  appears  in  dis- 
tinct focus.     Before  focusing,  the  mirror  should  be  so  adjusted 
that  the  field  appears  brightly  illuminated ;  then,  after  focusing, 
it  will  probably  need  to  be  adjusted  still  further  in  order  to  obtain 
the  best  illumination.     The  direct  sunlight  should  never  be  em- 
ployed for  the  purpose,  but  diffused  light  from  the  sky  or,  better 
still,  if  it  can  be  obtained,  from  a  white  cloud.     If  lamplight  be 
employed,  it  is  well  to  correct  the  unpleasant  yellow  of  the  rays 
by  passing  them  through  glass  faintly  tinged  with  blue. 

(3)  Examining  now  the  object,  there  will  be  observed  a  rather 
fine  and  somewhat  irregular  network,  or  what  seems  to  be  such. 

<j*  ,/^jWhat  is  really  seen  is  an  aggregation  of  closed  sacs,  each  a  cell, 
placed  together  in  a  single  layer  and  in  such  a  way  that  there  are 
no  spaces  between  them.  The  cell-walls  are  so  nearly  transpar- 
em  JhAt  Jtjte  jnlf'  at  their  edges  where  they  join  or  merge  into  a 
C  •>..  common  wall  between  two  cells  that  one  is  able  to  see  them  with- 
"*  T*J(rs%iijfHug.  In  the-interior  of  the  cells  there  may  be  seen,  with 
care,  more  oAessft)fMninutely  granular  matter,  and  possibly  very 
faintly  a  larger  rounded  mass,  the  nucleus,  but  otherwise  the 
interior  appears  perfectly  transparent.  These  sacs,  however,  are 
by  no  means  empty,  nor  are  they  filled  with  air  or  other  gaseous 
matter ;  as  will  presently  be  shown,  they  are  filled  with  a  liquid 
or  semi-liquid  matter  which  is  invisible  only  because  it  is  color- 
less and  has  nearly  the  same  refractive  index  as  has  water. 


THE    TYPICAL    VEGETABLE   CELL.  285 

Without  changing  the  focus,  let  now  the  high  power  be  turned 
on  (the  one-sixth  or  one-eighth-inch  objective),  and,  by  means  of 
the  fine  adjustment,  let  the  cells  be  brought  into  accurate  focus. 
Fewer  cells  will  now  be  seen  in  a  single  view,  but  these  cells  will 
appear  very  much  larger,  and  the  granular  cell-contents  as  well  as 
the  cell-walls  will  be  much  more  distinctly  visible.  Not  all  the 
parts  of  a  cell,  however,  can  be  seen  at  once,  for  only  a  narrow 
space  measured  in  a  vertical  direction  can  be  in  focus  at  the  same 
time ;  to  explore  the  whole  cell  it  is  necessary  to  focus  up  and 
down  by  means  of  the  fine  adjustment.  The  nucleus  may  or 
may  not  be  distinctly  visible.  If  visible,  it  is  usually  but  faintly 
so,  by  reason  of  its  transparency. 

(4)  Eeversing  the  nose-piece  now,  and  bringing  the  low  power 
into  position  so  that  the  instrument  will  be  ready  for  the  next 
step  in  the  study,  the  slide  is  removed  from  the  stage,  the  cover- 
glass  is  taken  oif,  two  or  three  drops  of  the  strong  solution  of 
potassium-iodide  iodine  are  dropped  on  the  specimen,  and,  after 
allowing  the  liquid  a  few  minutes  to  penetrate,  the  cover-glass  is 
put  on  as  before ;  any  of  the  reagent  that  oozes  out  around  the 
edges  of  the  cover  is  now  soaked  up  by  means  of  blotting  paper, 
and  the  slide  is  replaced  on  the  stage  of  the  microscope.  Focusing 
upon  the  cells  now,  it  is  observed  that  the  cell-walls  have  scarcely 
been  stained  at  all,  but  the  protoplasm  and  nucleus  are  rendered 
distinctly  visible  by  reason  of  the  yellowish-brown  color  they 
have  acquired.  Iodine  thus  constitutes  one  of  the  tests  by 
means  of  which  are  recognized  protoplasm  and  other  proteid 
matters,  all  of  which  are  stained  yellowish-brown  by  it. 

It  is  observed  also  that  the  protoplasm  is  not  equally  distributed 
through  the  cell,  and  that  the  nucleus  sometimes  occurs  in  the 
centre,  sometimes  lodged  against  the  wall  of  the  cell,  and  some- 
times even  there  are  two  nuclei  in  a  cell.  Studying  these  phe- 
nomena more  particularly  with  the  high  power,  it  is  observed 
that  next  the  cell-wall  and  usually  closely  applied  to  it,  but  some- 
times slightly  pulled  away  from  it  by  the  osmotic  action  of  the 
test-liquid,  is  a  continuous  layer  of  protoplasm,  forming  a  kind 
of  inner  cell-wall.  This  is  the  primordial  utricle,  which  is  really 
made  up  of  an  outer,  less  granular  layer  called  the  ectoplasm, 
and  an  inner,  more  granular  one  called  the  endoplasm,  though 
it  is  not  easy,  except  with  the  most  careful  staining  and  the 


286  LABORATORY   EXERCISES   IN   BOTANY. 

best  light,  to  distinguish  these  layers  even  with  the  highest 
powers. 

Interior  to  the  primordial  utricle  are  seen  irregular  threads 
and  bauds  of  granular  protoplasm  connected  with  the  endoplasm 
on  the  one  hand  and  with  the  nucleus  on  the  other.  The  spaces 
between  these  threads  and  bands  are  sap-cavities  or  vacuoks.  The 
nucleus  usually  appears  as  a  rounded,  oblong,  or  sometimes  fusi- 
form mass,  of  denser  texture  than  the  rest  of  the  protoplasm,  and 
bounded  off  from  it  quite  sharply,  though  always  in  contact  with  it. 
The  nucleus  is,  in  fact,  enveloped  in  a  very  delicate  membrane. 
In  the  interior  of  the  nucleus  are  visible  one,  two,  or  sometimes 
more  rounded  spots,  of  different  density  from  the  rest,  called  the 
nucleoli. 

(5)  But  there  is  yet  to  be  learned  the  nature  of  the  cell-wall. 
Is  it  composed  of  cellulose,  is  it  lignified,  or  is  it  cutinized? 
Endeavor  is  made  to  answer  the  question  by  means  of  an  experi- 
ment. Again  reversing  the  nose-piece  so  as  to  bring  the  low 
power  into  position,  there  is  placed  at  the  edge  of  the  cover-glass, 
care  being  taken  not  to  get  any  on  the  upper  side,  a  single  drop  of 
a  mixture  consisting  of  strong  sulphuric  acid  2  parts  and  water 
1  part,  and  the  mixture  is  permitted  to  run  under  by  capillary 
attraction  and  to  come  into  contact  with  the  iodine-stained  sec- 
tion. The  effects  are  now  observed  under  the  microscope.  The 
walls  of  the  cells  affected  begin  to  assume  a  deep-blue  color, 
owing  to  the  conversion,  by  the  acid,  of  the  wall-substance  into 
a  starch-like  compound  called  amyloid,  which  is  immediately 
stained  blue  by  the  iodine  present.  This  change  of  color  is 
accompanied  by  a  decided  swelling,  which  continues  until  the 
cell-wall  is  dissolved  and  the  color  at  first  produced  disappears. 
Not  all  of  the  wall,  however,  is  colored  blue,  nor  is  all  dissolved. 
A  light  line  will  be  observed  bounding  off  the  cells  from  cadi 
other,  and  this  line  increases  in  size  as  the  action  continues. 
This  middle  portion  of  the  cell-wall  is  a  little  different  from  the 
rest  in  chemical  composition,  and  dissolves  more  readily.  I  Jut 
after  this  and  the  portion  stained  blue  have  wholly  disappeared 
there  remains  a  thin  pellicle  which  is  stained  a  deep-brown  color. 
This  is  really  the  outer  portion  of  the  walls  of  the  cells,  the 
cuticle  of  the  epidermis.  There  are,  then,  in  the  cell-wall  three 
substances,  chemically  different:  the  part  that  stains  blue  with 


THE   TYPICAL   VEGETABLE    CELL.  287 

iodine  and  sulphuric  acid,  called  cellulose ;  a  part  that  readily  dis- 
solves, but  does  not  stain — the  middle  lamella,  composed  chiefly 
of  insoluble  pectates ;  and  the  cuticle,  which  is  chiefly  composed 
of  a  substance  different  from  either,  called  cutin. 

Another  fact  observed  is  that  the  protoplasm  has  been  stained 
even  a  deeper  brown  than  before,  and  that  it  is  still  recogniz- 
able, though  disorganized,  after  the  cellulose  has  disappeared. 

Another  reagent,  even  better  for  the  recognition  of  cellulose 
and  for  distinguishing  between  it  and  cutin,  is  chloriodide-of-zinc 
iodine.  Let  there  be  mounted  a  fresh  portion  of  the  epidermis  of 
the  Onion  scale  in  a  few  drops  of  this  liquid,  taking  care  not  to 
dilute  the  latter,  and  permitting  a  few  minutes  to  elapse  before 
putting  on  the  cover-glass,  so  as  to  give  the  reagent  opportunity 
thoroughly  to  penetrate  the  cells.  As  before,  it  is  found  that  the 
walls  are  stained  blue,  but  less  intensely,  and,  though  swollen,  they 
are  not  dissolved.  The  cutinized  portion  of  the  cell-wall  is  also 
turned  brown,  but  this  is  best  seen  by  studying  a  transverse 
section. 

Sections  may  best  be  made  by  cutting  through  two  or  three 
scales  at  once.  Placing  one  or  two  of  these  sections  on  the  slide, 
treating  them  with  a  few  drops  of  the  reagent,  and  examining 
them  with  the  high  power,  it  will  be  found  that  the  cells  appear 
in  a  shape  very  different  from  that  observed  in  the  other  view. 
They  are  oblong  or  nearly  rectangular,  with  the  longest  diameter 
parallel  to  the  surface  of  the  scale ;  the  inner  and  radial  walls 
are  thin,  but  the  outer  wall  is  thickened,  and  it  is  the  exterior 
part  of  this  wall  that  has  acquired  the  brown  color ;  it  is  the 
cutinized  part,  or  cuticle. 

(6)  Beautiful  and  instructive  permanent  mounts  may  be  obtained 
by  the  following  method :  First,  let  there  be  stripped  off  portions 
of  the  epidermis,  and,  to  prevent  them  from  curling,  let  them  be 
spread  out  rapidly  on  slides  and  afterward  treated  with  alcohol  to 
kill  and  fix  the  protoplasm.  They  are  then  thoroughly  washed  in 
water  and  placed  in  Grenadier's  alum-carmine,  in  which  they  are 
allowed  to  remain  for  twenty-four  hours.  They  are  then  removed 
from  the  staining  fluid,  rinsed,  and  passed  through  weak,  strong, 
and  finally  through  absolute  alcohol,  then  placed  for  a  few  moments 
in  oil  of  cloves,  and  from  this  transferred  to  the  centre  of  a  slide, 
a  drop  of  xylol  balsam  placed  on  them,  and  the  cover  put  on, 


288  LABORATORY    EXERCISES   IN    BOTANY. 

care  being  taken  in  doing  so  not  to  entrap  air-bubbles.  The 
cell-walls  will  be  stained  red,  but  will  be  sufficiently  transparent 
to  allow  the  nucleus  and  the  protoplasm,  also  stained  red,  to 
be  seen  distinctly.  It  is  from  specimens  thus  treated  that  the 
accompanying  drawings  (PL  XXXVlII.)  have  been  made. 


THE  TYPICAL  VEGETABLE  CELL. 


PLATE  XXXVIII.,  FIG.  1.— Cells  of  Outer  Epidermis  of  Onion-scale  (magnified  200 
diameters) :  a,  nucleus ;  b,  primordial  utricle  shrunken  away  from  the  cell-wall  some- 
what by  the  action  of  the  alcohol ;  c,  space  between  cell-wall  and  primordial  utricle;  d, 
an  oil-globule,  which  may  best  be  seen  in  an  iodine-stained  section ;  e,  cell-wall ;  /, 
vacuole;  g,  granular  protoplasm. 

FIG.  2.— Transverse  Section  of  Epidermis  of  Onion-scale,  showing  thickening  of  ex- 
terior wall  and  cutinization  of  its  outside  portion.  The  unshaded  part,  a,  represents 
cuticle ;  the  shaded  parts,  b,  the  cellulose  portion  of  the  wall ;  c,  one  of  the  parenchyma- 
cells  beneath  the  epidermis.  The  walls  are  considerably  swollen,  the  drawing  having 
been  made  from  a  section  that  had  been  treated  with  zinc-chloriodide  iodine.  The  cell- 
contents  are  omitted  from  the  drawing.  (Magnification,  285  diameters.) 
19 


EXERCISE  II. 

TISSUES  OF  THE  HIGHER  PLANTS. 

SECTIONS  of  the  stems  of  almost  any  fern,  gymnosperm,  mono- 
cotyl,  or  dicotyl  will  afford  instructive  study,  for  in  all  these 
plants  are  found,  not  one  kind  of  cell  merely,  as  in  the  fila- 
mentous alga?,  for  example,  but  many  kinds,  diifering  from  each 
other  not  only  in  shape  and  in  size,  but  also  in  structure  and  in 
function.  These  different  kinds  of  cells  are  called  tissues.  The 
cells  of  the  Onion  epidermis  already  studied  really  constitute  a  tis- 
sue, but  they  are  only  slightly  modified  from  the  primitive  cell- 
type.  Many  of  the  other  tissues  are,  however,  strongly  modified 
— so  strongly,  in  fact,  that  they  have  largely  lost  their  cellular 
character,  and  at  maturity  serve  merely  a  mechanical  purpose  in 
the  plant.  There  is  every  gradation  between  these  two  extremes. 
The  different  kinds  of  tissues  are  fully  described  and  illustrated, 
and  their  relations  explained,  in  Part  II.  of  the  author's  College 
'otany,  to  which  the  student  is  referred  ;  but  here  is  repeated  only 
he  scheme  of  classification  that  will  serve  as  a  guide  in  the  prac- 
tical studies  to  follow  : 

f     1.  Parenchyma,  ordinary  soft  cellular  tissue. 

2.  Collenchyma,  or  thick-angled  tissue. 
(      I.  Parenchymatous  j     3-  Sclerotic  parenchyma,  or  stony  tissue. 

4.  Epidermal  or  boundary  tissue. 

5.  Endoderrnal  tissue. 

6.  Suberous  or  corky  tissue. 

7.  Wood,  or  libriform  tissue. 

8.  Tracheids,  or  vasiform  cells. 

9.  Ducts,  or  vascular  tissues : 

a.  Dotted  ducts ;  d.  Annular  ducts ; 

16.  Sealariform  ducts  ;    e.  Reticulate  ducts ; 
c.  Spiral  ducts ;  /.  Trabecular  ducts. 

I  10.  Hard  bast  or  bast-fibres. 
-  III.  Sieve  series,  including  only — 

11.  Sieve  or  cribriform  tissue. 
IV.  Laticiferous  series,  including — 

12.  Laticiferous  or  milk-tissues,  of  which  there 

are  two  varieties : 
o»  Simple,  and 
b.  Complex. 

291 


TISSUES. 


II. 


Prosenchyma- 
tous  series. 


292  LABORATORY    EXERCISES   IN    BOTANY. 

Of  the  above  tissues,  all  of  the  prosenchymatous  series  are  at 
maturity  destitute  of  living  protoplasm,  and  are  therefore  mechan- 
ical in  their  function  ;  so  also  are  sclerotic  and  suberous  tissues ; 
and  colleuchyma  and  eudodermal  tissues  are  partly  so.  The  stem-, 
leaves,  and  roots  of  almost  any  of  the  higher  plants  contain  sev- 
eral of  these  tissues,  sometimes  nearly  all  of  them,  but  a  l'c\v  are 
of  rare  occurrence. 

For  the  purpose  of  getting  a  general  idea  of  the  commonest 
and  most  important,  let  sections,  transverse  and  longitudinal,  of 
the  stem  of  the  common  Geranium  (Pelargonium  zonale,  \VUkL) 
be  studied. 

I.  TRANSVERSE  SECTION. — Having  made  a  section,  as  thin  as 
possible,  extending  from  the  outside  to  and  into  the  central  pith, 
it  is  placed  on  a  slide  and  treated  with  a  few  drops  of  the  zinc- 
chloriodide  iodine,  and  after  a  few  minutes  examined  under  the 
low  power. 

It  is  observed,  first,  that  there  are  tissues  whose  cell-walls  have 
stained  blue,  and  others  whose  cell-walls  have  stained  a  deep- 
brown.  It  is  observed  also  that  there  are  great  differences  of 
size  and  shape  among  the  cells,  differences  in  the  compactness  of 
their  arrangement,  and  differences  in  the  thickness  of  their  walls, 
as  well  as  great  differences  in  their  contents, 

(1)  On  the  very  outside  may  be  found  a  single  tier  of  closely- 
laid  and  similar  cells  interspersed  with  hairs  and  having  their 
outer  walls  thickened.  This  is  the  epidermis.  Beneath  it,  if  the 
stem  is  not  too  young,  are  several  tiers  of  tabular  or  brick-shaped 
cells  arranged  in  radial  rows.  The  members  of  the  outer  tiers  are 
empty,  or  at  least  contain  no  protoplasm,  and  their  walls  arc  stained 
brown.  The  inner  members  of  the  series,  which  are  younger,  may 
still  contain  protoplasm,  and  the  walls  may  show  some  blue  color. 
Tlii-  whole  series  of  tabular  cells  constitutes  the  cork-tissue  which 
has  formed  underneath  the  epidermis,  and  which  sooner  or  later, 
by  the  continuous  multiplication  of  its  cells,  will  push  the  epi- 
dermis off,  and  afterward  the  cork-cells  themselves  will  peel  on" 
at  the  surface.  It  is  this  peeling  off  which  gives  the  rough  ap- 
pearance to  the  exterior  of  the  stem  when  it  is  old.  Destruction 
of  the  epidermal  and  exterior  cork-cells  had  in  fact  begun  in  the 
specimen  from  which  the  drawing  (PL  XXXIX.)  was  made. 
Figure  1,  a  represents  the  corky  tissue. 


TISSUES    OF    THE    HIGHER    PLANTS.  293 

.  ^^ 

(2)  Underneath  the  cork  is  seen  a  tissue  composed  of  cells  quite 
different  in  shape  and  arrangement  from  the  cork-cells.    They  are 
rounded  or  somewhat  polygonal  in  outline ;  their  walls  are  not 
cutinized,  but  are  of  cellulose,  and  therefore  stain  blue  instead 
of  brown  with  the  zinc-chloriodide  iodine  reagent ;  they  are  not 
arranged   in  radial  rows ;    they   have   more  or  less  conspicuous 
thickenings  at  the  angles  where  they  join  other  cells ;  and  they 
are  rich  in  proteid  contents.     This  is  colleuchy ma-tissue,  repre- 
sented at  6  in  Figure  1  (PL  XXXIX.). 

(3)  Still  further  interior  is  found  a  much  greater  thickness  of 
cells,  different  from   the  rest.      They  are  larger  than  the  collen- 
chy  ma-cells ;    they  are   not   thickened   at  the   angles,   but  have 
small  angular  interspaces  instead ;  their  walls  are  thin  and  com- 
posed of  cellulose ;   and  they  are  rich    in    proteid   and  starchy 
contents.     This  is  parenchyma-tissue,  represented  at  c  in  Figure 
1  (PI.  XXXIX.). 

(4)  Interior  to  this  again  is  a  zone  of  much  smaller,  angular, 
and  very  thick-walled  cells  whose  walls  have  stained  a  deep-brown. 
The  cells  of  this  tissue  are  destitute  of  proteid  and  starchy  contents; 
they  are  also  very  compactly  arranged,  so  that  there  are  either 
no  intercellular  spaces  or  only  very  minute  ones.     These  thick- 
walled  cells  are  bast-fibres  constituting  a  variety  of  the  mechanical 
tissues,  and  their  walls,  like  those  of  most  other  mechanical  tissues, 
are  lignified.    With  the  reagent  that  has  been  employed  they  have 
been  stained  the  same  color  as  the  cork-cells,  but  their  chemical 
constitution  is  not  the  same,  as  may  readily  be  proved  by  means 
of  another  test  :  Let  a  fresh  section  of  the  same  stem  be  treated 
first  with  two  or  three  drops  of  the  phloroglticin  solution,  and 

r  a  few  moments  with  a  similar  quantity  of  hydrochloric  acid; 
the  section  is  then  covered  and  examined  :  the  bast-fibres  are  now 
found  to  be  stained  red,  while  the  cork-cells  remain  unchanged  in 
color.  The  bast-fibres  are  shown  at  d  in  Figure  1  (PL  XXXIX.). 

(5)  Next  the  bast-fibres,  on  the  side  toward  the  pith,  is  a  not  very 
broad  area  or  zone  of  small-celled  tissue  whose  walls  have  stained 
blue  with  the  chloriodide.     By  turning  on  a  higher  magnifying 
power  there  can  easily  be  distinguished  in  it  two  layers :  the  outer 
layer,  composed  of  somewhat  larger  cells  which  in  this  view  ap- 
pear more  rounded,  of  unequal  size,  and  which  are  not  arranged 
in  any  apparent  order,  constitutes  the  soft  bast,  made  up  chiefly 


294  LABORATORY    EXERCISES    IN    BOTANY. 

of  two  kinds  of  thin-walled  tissues — sieve-tissue  and  a  variety  of 
parenchyma;  the  inner  of  the  two  layers  is  composed  of  very 
minute  and  very  thin-walled  cells,  rich  in  protoplasm,  but  desti- 
tute of  intercellular  spaces,  and  the  cells  have  a  more  or  less  evident 
arrangement  in  radial  rows.  This  is  called  meristem -tissue,  and 
the  zone  of  it  which  occurs  here  at  the  junction  of  the  wood  and 
the  bark  constitutes  what  is  called  the  cambium  zone  of  the  stem. 
Meristem-tissue  is,  however,  not  really  a  separate  tissue,  but  con- 
sists of  very  young  cells,  some  destined  to  develop  into  one  kind  of 
tissue,  others  into  another.  In  the  illustration  e  and  /(Fig.  1,  PL 
XXXIX.)  are  respectively  the  soft  bast  and  the  meristem-tissues, 

(6)  Next  interior  to  the  cambium  zone  is  a  tissue-layer,  more 
or  less  broad  according  to  the  age  of  the  stem,  composed  of  cells 
the  majority  of  which,  in  this  view,   look  like   bast-fibres  and 
have  stained  the  same  color.     Sprinkled  among  these  cells  are 
others  of  larger  calibre,  but  whose  walls  are  thickened  and  like- 
wise stained  brown.     The  former  is  wood  or  libriform  tissue,  and 
the  latter  vasiform  tissue,  consisting  of  ducts  or  tracheids  of  vari- 
ous kinds.    Both,  like  the  bast-fibres,  are  mechanical  tissues,  their 
functions  in   the  stem  being  chiefly  those  of  strengthening  and 
conveying  nutriment. 

(7)  Interior  to  this  zone  of  wood,  as  it  is  called,  is  a  large-eel  led 
parenchyma  substantially  like  that  between  the  zone  of  cork  and 
that  of  bast-fibres  except  that  the  cells  are  mostly  larger :  this  is  the 
pith-parenchyma.     The  outer  layers  of  it  consist  of  smaller  cells 
more  compactly  arranged,  while  the  inner  part  is  composed  of 
relatively  large  cells  with  rather  conspicuous  intercellular  spaces. 
The   pith-cells  are  rich    in   starchy  contents,  but  often   contain 
but  little  protoplasm,  and  in  very  old  cells  there  is  none  at  all. 
Usually  from  these  the  starch  also  has  disappeared. 

II.  LONGITUDINAL  SECTION. — By  making  a  thin  section 
that  runs  lengthwise  of  the  stem  near  its  middle,  and  treating  it 
as  the  last  was  treated,  there  will  be  discovered  other  important 
differences  between  the  different  tissues.  But  first  the  method  of 
making  irood  longitudinal  sections  with  the  razor  should  he 
learned.  Let  first  a  piece  of  the  stem  from  three  to  five  centi- 
metres long  be  taken.  By  means  of  a  sharp  pocket-knife  the 
stem  is  cut  transversely  about  six  millimetres  hack  of  one  end  to 
a  trifle  beyond  its  centre;  then  the  knife-blade  is  withdrawn,  and 


TISSUES   OF   THE    HIGHER   PLANTS. 


295 


by  placing  it  at  the  end  of  the  stem  the  latter  is  split  down  to 
the  transverse  cut,  and  a  portion  extending  not  quite  to  the 
centre  is  removed  from  the  stem.  The  razor  should  not  be  used 
for  this  purpose,  because  of  the  danger  of  notching  it.  Now  let 
the  larger  portion  of  the  stem  be  taken,  and,  after  having  care- 
fully smoothed  off  with  the  razor  the  split  surface,  let  sections  be 
made  as  follows :  Using  the  unsplit  portion  of  the  stem  for  a 
handle,  and  extending  the  forefinger  to  guide  and  steady  the 
razor-blade,  it  will  now  not  be  difficult  to  cut,  with  a  steady, 
oblique,  pushing  motion,  a  few  thin  and  even  sections.  These 
should  immediately  be  transferred  either  to  water  or  to  alco- 
hol. The  blade  should  be  kept  wet  with  water  or  with  alco- 
hol while  cutting,  and  care  should  be  taken  that  the  sections 
run  directly  lengthwise  of  the  grain  and  not  far  from  the  centre 
of  the  stem.  Now,  by  means  of  a  brush,  let  one  of  the  sections 
be  transferred  to  a  slide,  and,  after  soaking  up  any  adhering 
liquid  with  blotting  paper,  immediately  cover  it  with  the  zinc- 
chloriodide  iodine,  and  after  a  few  minutes  examine  it.  Another 
section  should  be  treated  with  the  phloroglucin  reagent  and  be 
mounted  similarly. 

Studying  the  sections  now,  it  will  be  found  that  the  cork- 
tissue  does  not  look  very  different  in  this  view  from  that  seen  in 
the  transverse  section ;  the  collenchyma-cells,  however,  are  elon- 
gated in  the  direction  of  the  length  of  the  stem  ;  but  the  greatest 
difference  is  in  the  prosenchymatous  tissues,  the  bast-fibres,  wood- 
cells,  and  ducts  appearing  very  much  elongated  and  either  oblique- 
ended  or  taper-pointed.  Most  of  the  cells  of  the  soft  bast  and 
cambium  are  also  observed  to  be  several  times  as  long  as  broad. 

The  student  should  now  study  by  similar  methods  some  other 
of  the  kinds  of  stems  mentioned  at  the  opening  of  this  exercise, 
and  note,  by  means  of  drawings  and  otherwise,  the  result  of  his 
work. 


TISSUES   OF   THE   HIGHER   PLANTS. 


297 


PLATE  XXXIX.,  FIG.  1.— Portion  of  Cross-section  of  Stem  of  Pelargonium  zonale,  ex- 
tending from  the  exterior  to  the  pith,  and  showing  all  the  different  kinds  of  tissues  :  a, 
cork-tissue  exfoliating  at  the  surface  ;  b,  collenchyma ;  c,  cortical  parenchyma  ;  d,  bast- 
fibres  ;  e,  soft  bast ;  /,  cambium  zone  ;  g,  zone  of  wood  consisting  of  wood-cells  and  ducts 
of  various  kinds;  h,  small  parenchyma-cells  at  outer  border  of  pith  ;  i,  large  parenchyma- 
cells  forming  main  portion  of  pith. 

FIG.  2.— Portion  of  Longitudinal  Section  of  another  and  somewhat  younger  Stem  of 
the  same  species  :  the  letters  a  to  i,  inclusive,  refer  to  the  same  parts  as  in  the  previous 
figure ;  k,  the  epidermis,  in  this  specimen  not  yet  displaced  by  the  cork-cells  forming 
beneath ;  I,  a  glandular  hair ;  ra,  an  ordinary  hair.  (Both  figures  magnified  about  50 
diameters.) 


EXERCISE  III. 

« 

STUDY- OF  PAKENCHYMA. 

ORDINARY  parenchyma  is  a  very  abundant  tissue,  and  may  be 
studied  to  advantage  in  the  roots,  stems,  and  leaves  of  almost 
any  flowering  plant  or  fern.  In  herbs  and  aquatics  it  constitutes 
by  far  the  largest  proportion  of  the  plant ;  in  woody  plants, 
though  much  less  abundant,  it  still  exists  in  considerable 
quantity. 

Besides  the  ordinary  form  there  are  several  varieties  or  modi- 
fications, such  as  stellate  parenchyma,  where  the  cells  are  star- 
shaped;  folded  parenchyma,  where  the  walls  have  internal  folds; 
spongy  parenchyma,  where  the  cells  are  very  loosely  arranged  ; 
palisade  parenchyma,  where  the  cells  are  elongated  and  arranged 
somewhat  like  the  posts  of  a  palisade ;  and  pitted  parenchyma, 
where  the  walls  are  pitted  or  marked  by  thin  places  of  various 
dimensions  and  shapes  in  different  cells.  Ordinary  and  pitted 
parenchyma  will  be  studied  in  this  exercise;  the  rest,  farther 
along  in  the  course. 

I.  ORDINARY  PARENCHYMA  OF  PUMPKIN  STEM. — Making  a 
thin  transverse  section,  mounting  it  in  a  few  drops  of  potassium- 
iodide  iodine,  and  examining  it  under  a  low  power,  it  is  ob- 
served— 

(1)  Parenchyma  is  the  most  abundant  tissue  of  the  stem  ;  it  con- 
sists of  thin-walled,  rounded  or  polygonal  cells  having  small  angu- 
lar intercellular  spaces,  the  cells  being  rich  in  protoplasm.  These 
facts  agree  with  what  has  already  been  observed  in  the  paren- 
chyma of  the  Geranium  stem  ;  they  agree  also  with  the  structure 
of  ordinary  parenchyma-tissue  in  general.  If  a  longitudinal  sec- 
tion be  made  and  the  tissue  be  examined,  it  will  be  found  that 
in  this  view  it  does  not  appear  markedly  different  from  that  in 
the  transverse  section  ;  the  cells,  that  is,  are  not  much  longer 

mn  broad,  and  are  blunt-ended,  as  is  usually  the  case  with  par- 

299 


300  LABORATORY    EXERCISES    IX    BOTANY. 

enchyma-cells.  Ordinary  parenchyma-cells  may  sometimes  In- 
found  that  are  two,  three,  or  in  rare  instances  even  several  times 
as  long  as  broad,  but  even  then  they  are  blunt  or  square-ended, 
not  acute,  oblique,  or  taper-pointed. 

(2)  As  the  walls  have  not  been  stained  by  the  reagent  used,  it 
may  be  inferred  that  they  are  composed  of  cellulose,  and  then-- 
fore would  probably  stain  blue  with  the  chloriodide-of-zinc  iodi-ie. 
Since  this  reagent  will  aid  to  further  knowledge  of  the  structure 
of  the  tissue,  a  new  section  should  be  prepared  and  be  treated 
with   the   chloriodide  on    another  slide.       After  the  blue   color 
characteristic  of   cellulose   has   been   developed   in   the  walls,  it 
will  readily  be  seen,  if  the  high  power  be  turned  on,  that  the 
walls  are  not  uniformly  colored,  but  appear  punctate  with  nearlv 
colorless  dots.     These  dots  are  not  apertures,  as  might  at  first 
be  supposed,  but  are  thin  places  in  the  wall,  consisting  really  of 
little   more  than  middle  lamella.      It  is  learned   from  the  test 
that,  thin  as  the  walls  of  the  cells  are,  they  are  not  of  even 
thickness.     This  is  true  of  the  walls  of  all   cells  which  have 
reached  maturity,  but  the  inequality  is  usually  greatest  in   the 
walls  that   have    become  considerably  thickened,   and   it  is  by 
reason  of  this  fact  that  some  thickened  cell-walls  have  very  con- 
spicuous markings,  such  as  pits,  bars,  spirals,  and  so  on. 

(3)  Returning  now  to  the  section  that  was  treated  with   the 
potassium-iodide  iodine,  let  the  cell-contents  be  studied.     It  \\  ill 
be  found,  as  was  done  in  the  cells  of  the  Onion  scale,  that  the 
cells  contain  protoplasm  and  a  nucleus,  and  in  these  may  l>e  dis- 
tinguished nearly  the  same  structure.     On  the  outside  is  the  pri- 
mordial utricle,  which  in  places  has  been  shrunken  away  from  the 
cell-wall  by  osmosis ;  in  the  centre,  or  sometimes  in  contact  with 
the  wall  of  the  cell,  is  the  rounded,  distinctly  outlined  nucleus, 
containing  two  or  more  nucleoli ;  there  are  the  plates  and  bauds 
of  protoplasm  connecting  the  nucleus  with  the  primordial  utricle; 
and  between   the  plates  and   bands  are  sap-spaces  or  vacuolcs. 
Here,  as  in  all  protoplasm,  are  found  very  minute  granules,  the 
microtomes. 

Besides  the  microsomes  there  are  other  granules,  rounded  or 
in  form,  of  much  larger  size,  and  stained  brown  like  the 
asm   ;md    nucleus,  only  deeper,  because  they  arc  denser. 
They  are  the  chlnm^lt^t^  or  chlorophyll-bodies;  in  the  fresh  >teiu 


STUDY    OF    PARENCHYMA.  301 

they  are  green  in  color  by  reason  of  the  chlorophyll  they  contain. 
It  is  the  coloring  matter  in  these  chloroplasts  which  gives  the  green 
color  to  the  leaves  and  other  green  portions  of  the  plant. 

There  are  other  granules,  dense,  rounded,  and  stained  so  deeply 
as  to  appear  black  with  the  strong  iodine  solution  used  :  these  are 
of  an  entirely  different  nature,  not  proteid  at  all,  but  starch- 
grains,  as  may  readily  be  proved  by  using  on  a  fresh  section  a 
little  of  the  iodine  solution  much  diluted  with  water,  when  they 
will  show  their  proper  blue  color.  Or  the  same  object  may  be 
compassed  even  better  by  the  use  of  a  few  drops  of  the  chloral- 
hydrate  iodine,  which  dissolves  the  proteids  and  causes  the  starch- 
grains  to  swell  slowly,  at  the  same  time  staining  them  the  charac- 
teristic blue  color. 

If  the  parenchyma  examined  is  from  near  the  outside  of  the 
section,  it  will  be  found  that  the  chlorophyll  bodies  are  numerous  ; 
if  from  farther  interior,  few  or  none  will  be  seen,  while  here  the 
starch-grains  are  usually  more  abundant. 

II.  PITTED  PARENCHYMA  FROM  THE  STEM  OF  THE  SAGO 
PALM  (Cycas  revoluta). — This  modification  of  parenchyma, 
though  much  less  common  than  that  just  described,  is  still  easy 
to  observe,  being  found  in  the  pith  of  many  woody  plants,  as  in 
that  of  Pilocarpus  selloauus,  Engler,  P.  Jaborandi,  Holmes, 
Asimiua  triloba,  Dunal,  Magnolia  grandiflora,  L.,  and  Magnolia 
glauca,  .L.,  in  the  parenchyma  between  the  bundles  in  the  stems 
of  most  woody  monocotyls,  and  in  the  medullary  rays  of  a  large 
proportion  of  the  woody  dicotyls. 

(1)  If  a  transverse  section  of  the  petiole  of  the  Sago  Palm  be 
made,  and  merely  mounted  in  water  without  staining,  it  will  be 
seen  that  the  rather  thick-walled  parenchyma  shows  many  trans- 
parent, rounded  or  oblong  areas,  that,  being  colorless,  look  like 
perforations.    They  are  not  perforations,  however,  but  are  merely 
thin  places  perfectly  analogous  to  those  already  observed  in  the 
thin-walled  parenchyma  of  the  pumpkin  stem ;  only  here,  owing 
to  the  much  greater  thickening  of  the  rest  of  the  wall,  they  are 
more  conspicuous.     They  even   give  to  the  edges  of  the  cell  a 
distinctly  beaded  appearance. 

(2)  If  the  cover-glass   be  taken  off  and  the  phloroglucin  or 
aniline-chloride  test  be  applied,  it  will  probably  be  found  that  the 
thickened  walls  of  the  parenchyma-cells  are  also  somewhat  ligni- 


302  LABORATORY    EXERCISES    IX    BOTANY. 

fied,  though  not  nearly  so  strongly  as  the  wood-cells  and  ducts 
which  may  he  seen  in  the  same  section. 

(3)  A  still  better  idea  of  the  structure  of  these  cells  will  be 
obtained,  however,  if  some  new  sections,  both  longitudinal  and 
transverse,  are  made  and  are  treated  as  follows:  If  the  sections 
are  cut  from  fresh  tissues,  they  should  be  plunged  into  alcohol  or 
acetic  alcohol  for  a  few  moments  to  fix  the  protoplasm  and  to  facil- 
itate staining;  they  are  then  washed  in  water  and  placed  for  about 
fifteen  minutes  in  a  dish  containing  a  little  of  the  gentian-violet  solu- 
tion ;  they  are  again  washed,  this  time  in  alcohol,  to  remove  the 
excess  of  stain,  in  the  last  washing  causing  them  to  pass  through 
absolute  alcohol  so  that  they  become  anhydrated,  and  are  then 
laid  for  fifteen  or  twenty  minutes  in  eosin  oil  of  cloves,  which  both 
clears  the  section  and  removes  most  of  the  gentian-violet  that  is 
left  in  the  cellulose  tissues,  while  at  the  same  time  it  communicates 
its  own  color  to  them.  The  thicker  portions  of  the  wall  are  now 
found  to  have  retained  the  violet  color,  while  the  thin  portions  arc 
unstained  by  it,  but  are  distinctly  colored  by  the  eosin,  thus  prov- 
ing that  they  are  not  perforations. 

The  staining  also  reveals  the  fact  that  the  cells  contain  proto- 
plasm and  a  nucleus. 

Between  this  rather  thick-walled  and  distinctly  pitted  paren- 
chyma and  the  ordinary  kind  there  are  found  in  different  plants, 
or  often  even  in  the  same  plant,  everv  gradation  ;  and,  on  the 
other  hand,  there  may  also  occur  every  gradation  between  it  and 
sclerotic  tissue,  soon  to  be  studied. 


STUDY   OF   PARENCHYMA. 


303 


PLATE  XL.,  FIG.  1.— A  small  portion  of  the  Parenchyma  as  seen  in  a  transverse 
section  of  the  stem  of  the  Pumpkin  (magnification  about  60  diameters) :  a  and/,  chloro- 
plasts ;  b,  the  nucleus ;  d,  ordinary  protoplasm  ;  e,  small,  angular  intercellular  space ;  g, 
a  starch-grain. 

FIG.  2.— A  small  portion  of  the  Cell-membrane  of  one  of  the  Parenchyma-cells  (mag- 
nified 500  diameters),  showing  the  small  pits.  The  drawing  was  made  from  a  section 
which  had  been  stained  by  means  of  zinc-chloriodide  iodine,  a,  one  of  the  pits. 


STUDY   OF   PARENCHYMA. 


305 


PLATE  XLL— A  few  Cells  of  Pitted  Parenchyma,  drawn  from  a  longitudinal  section 
of  the  petiole  of  Cycas  revoluta  (magnification  about  210  diameters) :  a,  one  of  the  thin 
places  or  pits ;  b,  space  where  a  portion  of  the  wall  has  been  cut  away  by  the  section- 
kiiife ;  c,  intercellular  space ;  d,  one  of  the  pits  seen  edgewise  in  the  cell-wall. 

20 


EXERCISE  IV. 

STUDY  OF  COLLENCHYMA. 

THE  following  objects  are  easily  obtainable,  and  afford  conve- 
ient  examples  for  study  :  the  petioles  of  almost  any  species  of  the 
Itivated  Begonias ;  those  of  almost  any  species  of  Grape,  of  the 
umach,  of  Burdock,  of  Pie-plant,  and  of  Plantain  ;  the  stems 
f  the  Yellow  Dock,  the  Pumpkin,  the  Ohio  Buckeye,  of  Joe- 
'ye  Weed   (Eupatorium  purpureum,   L.) ;    and  the  stems  and 
tioles  of  Spikenard  (Aralia  racemosa,  L.). 

THE  PETIOLE  OF  BEGONIA  DISCOLOR  (H.  K.),  a  common 
nhouse  plant,*will  be  the  subject  of  the  present  study.  Let 
transverse  section  first  be  made,  as  thin  a  one  as  possible,  and 
ounted,  without  exerting  pressure  on  the  cover-glass,  in  a  few 
rops  of  the  strong  potassium-iodide  iodine  solution.  •  Care 
hould  always  be  taken,  especially  in  the  study  of  fresh  or 
nhardened  sections  of  delicate  tissues,  not  to  put  on  the  cover- 
lass  in  such  a  way  as  to  exert  more  than  the  minimum  of  pressure 
the  section,  otherwise  the  cells  will  be  crushed  or  inclined  to 
ne  side,  making  it  difficult  to  understand  the  structure.  Hav- 
g  obtained  a  successful  mount,  let  it  be  examined  first  with  the 
w  power  and  afterward  with  the  high  one. 
(1)  At  the  very  periphery  of  the  section  is  seen  the  epidermis, 
nsisting  of  a  single  tier  of  cells,  and  immediately  beneath  or  in- 
ner to  this  is  the  tissue  to  be  studied — the  thick-angled  tissue, 
r  collenchyma.  It  consists  usually  in  this  species  of  about  five 
six  layers  of  cells  of  varying  sizes,  but  averaging  considerably 
r  than  those  of  the  epidermis  exterior  to  them,  and  smaller 
an  those  of  the  parenchyma  interior  to  them. 
It  is  in  this  position — namely,  just  interior  to  the  epidermis  or 
)  the  cork  that  may  be  formed  from  it — that  collenchyma,  when 
present  at  all,  is  usually  found.  It  very  rarely  occurs  else- 
where in  the  plant.  It  is  pre-eminently  a  strengthening  tissue 
to  the  epidermis,  and  sometimes,  as  in  the  present  instance,  forms 
a  continuous  band  or  zone  about  the  sublying  tissues ;  at  others 

- 


I.A|'.'>I:.VIOI:Y    I.  \  li:-  I-K.-    IN    i;oT,\NV. 


it  i»    Intermpted    at   interval-,   and    form-    lon^r   band-   or 

running  l<u^tli\\  ise  of  the  organ,  as  in  tin-  .-h-m  of  Yellow  l>ock 
ami   in  the  -terns  and  petioles  of  many  Umbellifer;,.. 

(2)  The  mo-t  distinguishing  characteristic  of  <•<>!!<  -ncliyma  i- 
readily  .-ecu  —  namely,  the  thickened  an;jl<  •-  "I"  tin-.  cell-.  Th<  •-<• 
thickenings  in  most  cases  are  great  enougli  to  obliterate  com- 
pletely tli«-  intercellular  space,  though  sometime-  ;,  portion  of  this 
.-till  remains,  as  may  often  be  seen  in  the  petiole-  of  Pie-plant.  In 
some  plants  these  thick  en  in--  are  excessive,  so  a-  -tron^ly  to  en- 
croach upon  the  lumen  of  the  cell  ;  in  other  in.-tance-  they  are  },nt 
slight.  In  K>me  species  the  thickening  is  confined  to  the  au-jle-, 

\vliile  in  f.tlier-  it  may  extend,  to  a  less   degree,  to  tin-  entire  wall. 

It  is  easily  determined,  by  aid  of  the  sulphuric-acid-and-iodinc 
or  by  the  chloriodide-of-zinc  iodine  test,  that  the  ihiekenin-j- 
in  the  |ij-(-»-nt  in-taiiee  are  of  eellulose,  and  not  of  ii^nin  ;  and 
thi-  i-  ii-iially  the  case  witli  this  tissue,  though  in  a  fl-\v  instances, 
where  the  thickenings  are  excessive,  there  is  more  or  less  of 
ligniflcation, 

I'nder  a  hi^h  power  dclieatc  stratification-lines  may  be  ob- 
served in  th<;  more  prominent  thickenings.  These  are  common 
in  thickened  walls  generally,  and  arc;  due  to  dill'm-in-i-  in  the 
amount  of  water  contained  in  different  layers,  makiir.;  some  more 
t  can-parent  than  others.  That  this  is  the  case  may  be  demon- 
strated by  removing  the  water  completely  by  treatment  with  a 
•  •on-iderable  quantity  of  absolute  alcohol,  when  the  line-  di-ap- 

'i'here  are  al.-o  other  way-  of  proving  the  name  tlm 
will    be   denr.n-lrated    in    a    future   exercise. 

(:\)  The    iodine  test   shows  that  these   cells,  like    the    paivn- 

chyma-c,.||-    farther    interior,    c(,ntain    protopla-m,    a    nucleus,  and 

chUwophy  11  -bodies.     Tln-\-  are  therefore   not    merely  mechanical 

li  ii'  .  but  take  an  active  part  in  the  vital  processes  of  the  plant. 
Occasional  cells,  usually  larger  than  the  rest,  are  -ecu  to  con- 
tain -Icllafe  ,,ia--e-  of  crv-tal-.  If  to  a  fr«--h  Action  there 
be  applied  two  or  three  drop-  of  -troii'_r  aceiie  aeid.  it  \\ill  b<; 
Ibnnd  that  even  after  ^mie  time  i  ils  remain  nnall'  • 

but  if  t.,  a  -imilar  section  a  (i  -\\-  drop-  of  -troii^  h\  droehloric  aci<l  be 

applied,   the    .  -olve    without     en'erve-criice.        |I;,,| 

been  rnmpo-id  of  calcium    carbonate.  ihe\    would  ha\e  ell'er- 
d    and    pa--c<|    into   solution    in    both    acid.-;    had    the\ 


srri>y    OK 


i  Kvii  v  MA. 


composed  of  silica,  they  would  not  have  been  a  fleeted  bv  cither. 
Since,  therefore,  it  is  known  that  calcium  oxalate  is  soluble  with- 
out efl'ervescenee  in  hydrochloric  acid,  but  not  in  acetic  acid,  the 
conclusion  is  that  the  crystals  arc  of  this  substance — the  common- 
est by  far  of  all  the  crystalline  substances  in  plant-cells. 

11.   LONGITUDINAL    Yir.w    OF    COLLENUIYMA. — l^ot  there 

>w  be  made  a  longitudinal  section  of  the  petiole  nearly  through 
ctMitre,  in  the  same  manner  as  directed  in  Kxercise  11.  ('arc 
mst  be  observed  to  cut  the  sections  very  thin,  otherwise  the 
•nctnre  cannot  well  be  seen,  owin^  to  the  overlapping  of  the 
Is.  The  sections  should  now  be  treated  with  ehloriodido-of- 
inc  iodine,  so  that  the  cell  walls  may  easily  be  traced.  The 
Mgitudinal  view  of  the  tissue  appears  quite  different  from 
transverse  view,  partly  because  of  the  thickenings —which 
now  seen  lengthwise,  appearing  as  long,  narrow  bands — 
partly  because  the  cells  themselves  are  considerably  elon- 
d  in  the  direction  of  the  section.  As  to  their  length,  hoxv- 
•,  they  difl'er  much  among  themselves.  Some  arc  no  more 
lan  t \\ice  as  long  as  broad,  while  others  may  have  a  length  (ive 
six  times  the  thickness.  It  will  be  observed  that  the  narrower 
11-  are  nsnallv  the  longer,  as  though  \\liat  had  been  gained  in 
ngth  had  been  sacrificed  in  thickness.  The  cells  containing 
sials,  being  of  great  transverse  diameter,  arc  also  short.  It 
be  observed,  furthermore,  that  the  cells  are  blunt-ended, 
taper-pointed,  agreeing  in  this  respect  with  paronohyma- 
In  tact,  the  tissue  as  it  occurs  in  this  plant  is  not.  very 
ly  modified  from  ordinary  parenchyma.  In  some  other 
ilants  however,  it  is  found  tending  strongly  lo\\ard  fibrous 
siu».  Its  cells  are  <j;reatlv  elongated,  the  walls  much  thicker, 
(lids  more  inclined  to  oblique  or  tapering  forms,  and  in  some 
the  walls  oven  somewhat  lignified,  forming  a  tough  and 
ig  tissue  more  exclusively  devoted  to  mechanical  functions. 


STUDY    OF    COLLENCHYMA. 


311 


PLATE  XLIL— Small  portion  of  Petiole  of  Begonia  discolor  (transverse  section,  mag- 
nified about  210  diameters) :  a,  epidermal  cell ;  6,  nucleus  of  a  collenchyma-cell ;  c, 
thickened  angle  of  the  collenchyma-tissue  ;  d,  mass  of  crystals  of  calcium  oxalate  in  a 
large  collenchyma-cell ;  e,  a  chloroplast. 


EXERCISE  V. 

STUDY  OF  SCLEROTIC  PARENCHYMA. 

GOOD  examples  for  study  occur  io  most  of  the  nuts,  particu- 
larly the  Hickory-nut,  Pecan,  Hazel-nut,  English  Walnut,  and 
Cocoanut ;  in  the  flesh  of  the  Pear,  the  gritty  particles  in  which 
consist  of  this  tissue ;  in  the  pith  of  the  stem  of  Menispermum 
canadense,  L.,  and  in  that  of  the  Apple  twig ;  in  the  leaves  of 
Tea  and  Camellia ;  in  the  stem-barks  of  Ceylon  cinnamon  (Cin- 
namomum  Zeylanicum,  Breyne),  the  Sweet  Bay  (Magnolia 
glauca,  L.),  the  Umbrella  Tree  (Magnolia  Umbrella,  Lam.\  the 
Flowering  Dogwood  (Cornus  florida,  L.),  and  the  Custard  Apple 
(Asimiua  triloba,  Dunal) ;  and  in  the  root-barks  of  the  Dogbane 
(Apocyntim  androssemifolium,  £.),  the  Butterfly  Weed  (Asclepias 
tuberosa,  L.\  the  Yellow  Dock  (Rumex  crispus,  L.),  and  the 
Hop  tree  (Ptelea  trifoliata,  L.). 

Sclerotic  tissue,  often  from  its  hardness  called  "  stony  tissue," 
is,  as  found  in  the  shells  of  nuts,  for  example,  very  difficult  to  cut 
without  resorting  to  some  softening  process.  Softening  may  be 
accomplished  by  soaking  the  tissues  for  a  week  or  more  in  a  5 
or  10  per  cent,  aqueous  solution  of  potassium  hydrate,  and  then 
washing  out  the  alkali  by  means  of  clean  water  or  water  which 
has  been  slightly  acidulated  with  acetic  acid.  Good  sections  may 
now  be  cut  with  a  razor,  even  of  such  hard  structures  as  the 
shells  of  the  Hickory-nut  or  Cocoanut,  without  much  danger  of 
notching  the  blade,  providing  it  be  not  allowed  to  run  too  deep. 
The  darkening;  of  the  tissue,  which  is  often  one  of  the  results  of 

o 

the  process,  may  be  corrected  either  by  treating  the  sections  with 
the  sulphurous-acid  alcohol  described  in  the  Introduction,  or  by 
bleaching  them  with  Labarraque's  solution,  taking  care  to  carry 
the  bleaching  process  only  so  far  as  to  get  rid  of  the  coloring 
matters.  The  sections  may  then  be  washed  thoroughly,  stained 
with  safranin  solution  or  with  a  solution  of  iodine-green,  anhy- 

313 


314  LABORATORY    EXERCISES   IN    BOTANY. 

drated  by  means  of  absolute  alcohol,  and  permanently  mounted 
in  balsam. 

But  for  the  laboratory  a  method  which  is  less  time-consuming 
is  more  desirable,  hence  the  following  may  be  adopted  :  With  a 
thoroughly  sharpened  pocket-knife  cut  a  number  of  thin  sections 
parallel  to  the  surface  of  the  shell,  and  place  these  sections  by 
themselves  in  a  dish  of  water.  It  does  not  matter  that  they  are 
of  small  size  or  fragmentary  if  they  are  cut  thin.  After  soak- 
ing for  a  few  minutes  in  the  water,  particularly  if  it  be  heated 
to  near  the  boiling-point,  the  sections,  which  usually  roll  up  in 
cutting,  may  be  flattened  out  by  means  of  dissecting-needles  or 
by  means  of  a  needle  and  a  brush,  and  then  be  mounted  in  a 
drop  of  water  or  glycerin,  and  examined.  The  edges  at  least 
will  be  transparent  enough  to  permit  of  the  cells  being  seen  dis- 
tinctly. 

(1)  For  this  study  the  shell  of  the  Cocoanut  is  selected,  and  by 
means  of  the  process  last  described  a  dozen  or  more  sections  are 
cut  parallel  to  the  surface  of  the  nut,  and  as  many  from  the  edge 
of  a  broken  piece,  or  perpendicular  to  the  surface.  One  or  two 
sections  of  each  kind  are  now  mounted  on  different  slides. 

The  section  made  parallel  to  the  surface  is  first  examined. 
Focusing  with  the  low  power  upon  the  thinnest  part,  there  is 
seen  a  mass  of  cells  which  are  rounded,  somewhat  polyhedral,  or 
slightly  elongated  in  form,  pressed  so  close  together  that  no  in- 
tercellular spaces  are  visible,  and  having  excessively  thick  walls. 
On  or  in  the  walls  are  seen  minute  dots  or  punctulations,  as  well 
as  radial  lines  connecting  the  very  small  cavity  or  lumen  of  the 
cell  with  the  middle  lamella.  Many  of  the  lines  are  simple, 
while  others  branch  before  reaching  the  exterior.  With  the  high 
power  and  under  favorable  illumination  one  may  readily  con- 
vince one's  self  that  the  lines  are  really  minute  tubes  beginning 
at  the  lumen  and  terminating  at  the  middle  lamella.  The  dots, 
too,  are  of  the  same  nature,  as  may  be  learned  by  focusing  up 
and  down ;  they  are  small  tubes  looked  at  endwise,  and  there- 
fore appearing  round  or  dot-like.  The  tubes  may  be  rendered 
more  distinct  by  flattening  out  one  of  the  sections  on  a  slide, 
drying  it  over  an  alcohol  lamp  so  as  to  expel  the  water  from  the 
tubes  and  lumen,  putting  on  a  drop  of  balsam,  and  coveriiiLT 
with  a  cover-glass.  The  tubes  are  now  easily  traceable  because 


STUDY   OF    SCLEEOTIC    PARENCHYMA.  315 

filled  with  air.  They  are  called  pore-canals,  and,  strange  as  it 
may  seem,  they  are  perfectly  analogous  to  the  pits  observed  on 
ordinary  parenchyma-cells.  They  are,  like  the  latter,  thin  places 
in  the  wall,  but  by  reason  of  the  excessive  thickening  of  the  rest 
of  the  wall  they  have  become  lengthened  into  tubes.  They 
probably  serve  the  purpose  of  facilitating  the  circulation  of 
nutritive  fluids  from  cell  to  cell.  A  further  evidence  that  this 
is  the  case  is  the  fact  that  the  termination  of  the  tube  in  the 
middle  lamella  is  nearly  always  opposite  one  in  an  adjacent 
cell;  that  is,  the  ends  are  separated  from  each  other  only  by 
the  middle  lamella. 

Employing  good  illumination  and  the  high  power,  it  will  be 
found  also  that  the  thickened  walls  show  delicate  stratification- 
lines  forming  a  series  of  concentric  curves  about  the  lumen.  If 
a  section  be  mounted  in  water,  and  then,  after  focusing  upon  a 
part  of  it  that  shows  the  cells  sharply  defined,  a  drop  of  chloral- 
hydrate  solution  be  allowed  to  run  under  the  cover-glass,  and  in 
the  mean  time  the  result  be  closely  watched  as  the  swelling  reagent 
comes  into  contact  with  the  walls,  it  will  be  seen  that  the  lines 
come  out  more  distinctly,  but  after  a  time,  owing  to  continued 
swelling,  they  become  less  distinct.  Cuprammonia  may  be  em- 
ployed in  the  same  way,  but  it  works  more  rapidly,  and  its  effects 
are  therefore  more  difficult  to  observe. 

Comparing  now  the  sections  made  perpendicular  to  the  surface 
with  those  already  studied,  it  will  be  found  that  there  is  but  little 
difference  except  that  the  cells  are  on  the  average  longer  in  the 
section  made  perpendicular  to  the  surface  than  in  the  other, 
though  rounded  and  elongated  forms  are  found  in  both  sections. 
In  form,  therefore,  the  cells  are  essentially  like  ordinary  paren- 
chyma-cells :  they  are,  in  fact,  parenchyma-cells  in  which  the 
thickening  process  has  been  carried  much  farther  than  in  the 
pitted  parenchyma  just  studied — so  far,  indeed,  that  the  lumen 
has  been  nearly  obliterated,  and  the  cell  has  ceased  to  take  part 
in  the  vital  processes  of  the  plant. 

Between  ordinary  parenchyma-cells  and  these  sclerotic  ones 
ivery  possible  gradation  is  found. 

(2)  Let  now  an  effort  be  made  to  ascertain  whether  the  thick  - 
ming  deposits  in  the  wall  are  of  cellulose,  like  those  of  colleu- 
lyma,  or  of  liguin.  The  application  of  the  phloroglucin  test  to 


316  LABORATORY    EXERCISES   IX    BOTANY. 

a  fresh  section  speedily  dispels  any  doubts  that  may  have  arisen 
on  the  subject,  for  the  walls  are  stained  a  deep-red,  the  character- 
istic reaction  for  lignin. 

This  tissue  therefore  grades  toward  the  mechanical  tissues  of  the 
prosenchymatous  series,  and  in  some  instances, 'where  the  cells  are 
elongated  and  even  fusiform  in  shape,  it  becomes  difficult,  if  not 
impossible,  to  tell  them  from  sclerenchyrna-fibres. 

(3)  There  may  be  learned,  in  connection  with  this  tissue,  the 
method  of  isolating  cells  by  means  of  Schulze's  process.  Also  in 
the  isolated  cells  the  variety  in  their  shapes  may  be  seen  more 
readily  than  when  studied  in  mass. 

A  few  of  the  sections  are  placed  in  a  small  porcelain  evaporat- 
ing-dish,  and  a  small  quantity  of  strong  nitric  acid  in  which  a 
few  crystals  of  potassium  chlorate  have  been  dissolved  is  poured 
upon  them.  Better  results  are  obtained  if  the  sections  be  allowed 
to  stand  in  the  cold  solution  for  fifteen  minutes  or  more,  to  give 
the  liquid  time  to  penetrate  to  all  parts  of  the  structure.  Heat  is 
then  applied  very  gently,  and  meantime  the  process  is  watched 
carefully.  The  sections  soon  turn  a  deep-brown  color,  and  pres- 
ently effervescence  begins.  Heat  should  thereafter  be  only  very 
cautiously  applied,  if  at  all,  and  when  the  brown  color  has  disap- 
peared from  the  sections  the  contents  of  the  dish  should  imme- 
diately be  poured  into  a  large  quantity  of  cold  water  to  stop 
further  action.  After  the  acid  has  been  mostly  removed  from 
the  sections  by  soaking  them  for  a  few  minutes  in  clean  water, 
they  may  be  stained  with  methyl-green  or  with  iodine-green  and 
be  mounted  in  clean  water,  when,  by  gently  tapping  the  cover- 
glass  with  a  needle-point,  the  cells  will  separate  readily  from  each 
other.  This  is  by  reason  of  the  fact  that  the  middle  lamella  is 
more  readily  soluble  in  this  reagent  than  is  the  rest  of  the  cell- 
wall. 

The  cells  may  easily  be  mounted  in  permanent  form  by  remov- 
ing the  cover-glass,  soaking  up  the  superfluous  water  with  blot- 
ting paper,  putting  on  a  drop  of  liquefied  glycerin  gelatin,  and 
again  covering. 


STUDY    OF   SCLEROTIC    PARENCHYMA. 


317 


PLATE  XLIIL,  FIG.  1.— A  group  of  Sclerotic  Parenchyma-cells  from  a  section  of  the 
Cocoaiiut  shell  (magnification  about  330  diameters).  The  section  was  tangential,  or 
made  parallel  to  the  surface  of  the  nut.  The  cells  to  the  right  show  both  the  pore- 
canals  and  the  stratification-lines,  while  from  those  to  the  left  the  latter  have  been 

litted  to  show  the  former  more  distinctly,    o,  lumen  of  a  cell;  b,  a  branching  pore- 

uial ;  c,  middle-lamella. 

FIG.  2.-A  portion  of  the  same  kind  of  Tissue  from  a  Radial  Section  (magnified  about 
400  diameters). 


EXERCISE  VI. 

STUDY  OF  EPIDEKMAL  TISSUE. 

THE  epidermis  may  readily  be  stripped  off  from  the  leaves  of 
any  of  the  following  plants,  which  therefore  afford  convenient 
objects  for  study  :  most  of  the  Cultivated  Lilies  ;  the  Garden 
Hyacinth ;  the  Tulip ;  most  of  the  cultivated  species  of  Amaryl- 
lis, Agapanthus,  and  Narcissus ;  Tradescautia  Virginica,  L. ;  some 
species  of  Sedum,  as,  for  example,  the  Common  Live-for-ever 
(Sedum  Telephium,  L.) ;  the  Gentians,  as  Gentiana  alba,  Muhl. ; 
and  some  of  the  cultivated  species  of  Begonia,  as  Begonia  dis- 
color, H.  K. 

In  other  instances,  where  the  epidermis  is  too  fragile  or  too 
closely  adherent  to  sublying  tissues  to  separate  readily,  good  prep- 
arations of  it  in  the  fresh  condition  may  still  be  made  by  care- 
fully scraping  away  with  a  knife-blade  the  tissues  next  to  the  epi- 
dermis until  the  chlorophyll-bearing  cells  are  removed. 

For  the  present  exercise  is  selected  the  epidermis  from  the  leaf 
>f  the  Tulip.  This  may  be  obtained,  in  pieces  of  sufficient  size,  in 
the  manner  described  in  the  case  of  the  Onion  scale.  Let  the  epi- 
dermis from  the  under  or  dorsal  surface  of  the  leaf  first  be  studied. 

(1)  After  transferring  a  piece  of  the  epidermis  to  the  centre  of 

slide  and  treating  it  for  a  few  minutes  with  the  strong  solution  of 
potassium-iodide  iodine,  it  is  covered,  and  examined  first  with  the 
low  and  then  with  the  high  power. 

It  will  be  seen  that  the  ordinary  epidermal  cells  are  arranged 
rery  much  as  in  the  Onion.  They  are  considerably  elongated  in 
the  direction  of  the  length  of  the  leaf,  the  ends  are  blunt,  and  the 
cells  are  so  arranged  as  to  leave  no  intercellular  spaces.  This  is 
true  of  ordinary  epidermal  cells  generally,  and  in  this  respect 

icy  differ  markedly  from  those  of  parenchyma-tissue. 

The  cells  are  rich  in  protoplasm.  The  primordial  utricle,  the 
mcleus,  the  nucleoli,  and  the  threads  and  bauds  of  protoplasm 
ire  all  as  distinctly  recognizable  as  in  the  cells  of  the  Onion 

319 


320  LABORATORY    EXERCISES   IN    BOTANY. 

epidermis  already  studied,  and  are  very  similar  in  appearance  to 
the  cells  of  the  latter.  The  vacuoles  are  also  abundant,  and 
many  of  them  form  transparent  globules  of  various  sizes. 

But  a  conspicuous  difference  is  the  presence  of  stomata,  or  so- 
called  breath  ing- pores — small  apertures  between  a  pair  of  crescent- 
shaped  cells  called  guard-cells.  These  pores  were  not  found  in 
the  epidermis  of  the  Onion  scale,  because  this  was  not  exposed  to 
the  light.  The  epidermis  of  the  colorless  scales  of  parasites,  of 
the  scales  of  ordinary  plants  where  not  exposed  to  light,  and  of 
roots  and  subterranean  stems,  ordinarily  does  not  possess  stomata, 
but  that  of  all  green  parts  of  plants  above  the  mosses  in  the 
scale  of  life  usually  possesses  them  in  abundance,  except  that  they 
are  often  absent  from  the  epidermis  of  the  upper  surface  of  leaves. 
The  stomata  are  the  openings  through  which  the  plant  gets  rid 
of  the  superfluous  water  it  takes  up  chiefly  through  its  roots, 
through  which  it  exhales  that  portion  of  the  disengaged  oxygen 
which  it  does  not  require,  and  through  which  it  takes  in  the 
carbon  dioxide  which  it  needs  for  food.  They  are  apertures 
which  also  automatically  dilate  or  contract,  or  even  completely 
close,  according  to  the  condition  of  the  atmosphere  and  the 
necessities  of  the  plant.  If  the  air  is  dry  and  there  is  need 
for  the  plant  to  conserve  its  moisture,  the  stomata  contract ;  if 
the  air  is  moist  and  the  plant  has  more  water  in  its  tissues  than 
is  needed,  they  expand.  The  mechanism  by  which  these  move- 
ments are  accomplished  will  presently  be  discussed. 

The  guard-cells  are  much  smaller  than  the  ordinary  epidermal 
cells  and  are  much  richer  in  proteid  matters,  containing,  besides 
a  crescent-shaped  nucleus  and  ordinary  protoplasm,  numerous 
chloroplasts  and  occasional  oil-globules.  The  chloroplasts,  it  will 
be  observed,  are  not  present  in  the  ordinary  epidermal  c<>lls. 
This  is  true  of  the  epidermis  in  most  plants — a  fact  which 
accounts  for  its  transparency. 

(2)  Let  now  a  transverse  section  of  the  epidermis  be  made — 
that  is,  a  section  through  it  which  is  perpendicular  to  the  longest 
diameter  of  the  leaf;  for  in  order  to  understand  the  structure  of 
a  stem  it  is  necessary  to  have  a  section  which  crosses  the  two 
guard-cells  near  their  middle,  and,  since  the  stomata  all  point  in 
the  same  direction — namely,  lengthwise  of  the  leaf — this  is  the 
only  section  which  will  serve  the  purpose.  It  is  necessary,  more- 


STUDY   OF    EPIDERMAL   TISSUE,  321 

over,  to  have  the  section  quite  thin.  It  is  readily  made  as  fol- 
lows :  Cut  out  of  the  leaf  a  piece  about  half  an  inch  square,  and 
orient  it  properly  between  the  flat  surfaces  of  two  pieces  of  elder 
pith.  Holding  the  combination  rather  firmly  between  the  thumb 
and  the  fingers,  very  thin  sections  may  be  cut  through  pith  and  all, 
and  those  of  the  leaf  may  be  picked  out  by  means  of  the  pincettes. 

The  pith  for  this  purpose  is  best  prepared  as  follows  :  Take  a 
piece  about  four  centimetres  long  and  halve  it  lengthwise,  not 
by  placing  the  edge  of  the  razor  across  one  end  and  forcing  it 
through  toward  the  other,  but  by  placing  it  parallel  to  the  length 
of  the  cylinder  and  cutting  it  as  nearly  as  possible  through  the 
middle.  The  danger  of  breaking  it  into  small  fragments  is  thus 
avoided.  Between  the  flat  surfaces  of  the  two  semi-cylinders 
thus  produced  is  placed  the  leaf  to  be  sectioned. 

The  sections,  as  soon  as  cut,  should  be  transferred  to  water  to 
prevent  the  entrance  of  air ;  but  care  must  be  taken  to  keep  the 
pith  dry  during  the  process  of  sectioning,  for  if  moistened  it  does 
not  cut  well. 

Having  prepared  thus  several  good  sections,  one  is  selected, 
and  by  means  of  a  camel's-hair  brush  is  transferred  to  a  slide  and 
mounted  in  a  drop  of  water.  Since  the  weight  of  the  cover- 
glass  is  sufficient  to  crush  and  spoil  a  section  so  delicate,  it  is  best 
that  the  slide  used  should  have  a  ring  of  cement  or  of  sheet  wax 
in  its  centre,  a  little  smaller  in  diameter  than  the  cover,  and  of 
sufficient  thickness  to  relieve  the  section  of  the  pressure. 

On  placing  the  preparation  under  the  microscope  now,  it  will 
be  found  that  the  epidermis  consists  of  a  single  layer  of  cells, 
which  in  this  view  are  squarish  in  outline,  quite  thick-wralled 
exteriorly  and  only  a  little  less  so  interiorly,  but  with  the  radial 
walls  rather  thin.  At  intervals  occur  cells  in  pairs,  smaller,  of 
different  shape,  and  with  more  granular  contents.  These  are  the 
guard-cells.  If  the  section  happen  to  run  squarely  through  their 
middle,  it  will  be  possible  to  see  the  stoma  or  opening  itself. 

Underneath  the  epidermis  are  found  relatively  large,  rounded, 
thiu-walled  parenchyma-cells  having  between  them  conspicuous 
intercellular  spaces  and  containing  numerous  chloroplasts.  The 
stomata,  it  will  be  observed,  always  open  into  a  large  intercellular 
space.  Owing  to  this  arrangement  the  outside  air,  when  the 
stomata  are  open,  is  in  free  communication  with  the  whole  inte- 

21 


322  LABORATORY    EXEIK  ISKS    IX    BOTANY. 

rior  of  the  leaf,  since  air  can  circulate  freely  through  the  inter- 
cellular spaces.  The  importance  of  this  fact  to  the  functions 
already  mentioned  will  readily  be  understood. 

But  while  there  is  this  free  communication  between  the  interior 
and  the  exterior  through  the  stomata,  the  walls  of  the  epidermal 
cells  are  all  highly  impermeable  to  water,  for  the  epidermis,  as 
would  be  found  by  testing  it,  is  strongly  cutiuized,  and  cutin  is 
of  all  vegetable  substances  one  of  the  least  permeable  to  water. 
The  function  of  cutinized  epidermis  in  preventing  excessive  evap- 
oration is  strikingly  shown  in  the  case  of  the  leaf  of  the  common 
Live-for-ever  and  in  that  of  Bryophyllum.  If  a  leaf  of  either 
be  plucked  and  exposed  to  the  sun  and  dry  air  even  for  a  con- 
siderable time,  it  scarcely  shows  signs  of  withering ;  but  if  the 
epidermis  first  be  stripped  off,  the  leaf  will  shrivel  and  dry  in 
the  course  of  a  few  minutes. 

(3)  Mechanism  of  the  Opening  and  Closing  of  the  Stomaio.— 
The  movements  of  the  guard-cells  by  means  of  which  the  aper- 
ture between  them  is  enlarged  or  contracted  are  effected  by  means 
of  their  hygroscopism — that  is,  by  their  power  to  take  up  moist- 
ure from  the  air  about  them  and  to  part  with  it.  When  the  air 
is  moist  the  guard-cells  imbibe  moisture  and  swell,  but  they  are 
so  placed  as  respects  the  other  epidermal  cells,  and  the  thicken- 
ings of  their  walls  are  so  adjusted,  that  in  swelling  the  cells  must 
bow  out  in  the  middle,  thus  increasing  the  size  of  the  aperture ; 
and  when,  on  the  other  hand,  the  air  is  dry  and  they  part  with 
moisture,  the  cells  become  flatter,  less  convex  on  the  outer  or  more 
remote  surfaces,  and  less  concave  on  the  inner  ones,  or  those  next 
the  aperture,  thus  either  diminishing  the  latter  or  closing  it  com- 
pletely. The  cross-section  shows  that  the  more  remote  walls  re- 
main quite  thin,  thus  permitting  a  movement  in  a  direction  paral- 
lel to  the  surface  of  the  epidermis  and  perpendicular  to  the  length 
of  the  guard-cells,  while  movements  in  other  directions  are  not  pos- 
sible. Careful  tests,  moreover,  show  that  while  the  outer  part  of 
the  cell-walls,  and  even  the  inner  part,  is  cutini/cd.  the  radial  walls 
are  not  only  not  cutinized,  but  are  quite  thin  throughout  a  con- 
siderable portion  of  their  extent,  so  that  they  can  ivadilv  take  up 
moisture  and  as  readily  part  with  it.  VWhon  the  stoma  is  rlu-rd, 
however,  only  cutinized  surfaces  are  presented  to  the  outer  air,  and 
evaporation  is  thus  shut  off. 


STUDY   OF    EPIDERMAL    TISSUE.  323 

(4)  How  does  the  Epidermis  of  this  Plant  differ  from  that  of 
Others? — It  would  take  too  long  to  answer  the  question  fully, 
but  some  of  the  most  important  differences  may  be  pointed  out : 

(a)  In  the  majority  of  cases,  as  in  this,  the  epidermis  consists 
)f  a  single  layer  of  cells,  but  in  some  it  consists  of  two  or  more. 

(6)  In  many  cases  the  epidermis  is  smooth,  as  in  this,  but  in  the 
lajority  it  is  hairy  or  glandular. 

(c)  In  most  of  the  higher  plants  the  ordinary  epidermal  cells 
are  free  from  chloroplasts,  as  in  this,  but  in  ferns  they  are  present. 

(d)  In  many  other  plants  besides  this,  particularly  of  the  mono- 
cotyls,  the  epidermal  cells  are  quadrilateral,  or  at  least  but  slightly 
wavy  in  outline,  but  in  the  majority  of  plants  they  are  strongly 
wavy  or  sinuous  in  outline. 

(e)  In  some  cases,  as  in  this,  the  inner  wall  is  nearly  as  strongly 
thickened  as  the  outer,  but  in  the  majority  the  outer  is  much  the 
more  strongly  thickened  and  cutinized. 

(/)  Great  differences  exist  in  the  number  of  stomata.  While 
the  variation  is  not  usually  very  wide  within  the  limits  of  the 
species,  different  species  often  differ  greatly  from  each  other  in 
this  respect.  For  example,  there  are,  according  to  Weiss,  in  the 
epidermis  of  the  under  side  of  the  Oat  leaf  2700  to  the  square 
centimetre,  while  in  the  under  side  of  the  leaf  of  the  Olive  there 
are  63,500  to  the  square  centimetre. 

(g)  There  are  differences  in  the  arrangement  of  the  stomata. 
In  some  plants  they  are  distributed  in  rows  running  lengthwise 
of  the  organ ;  in  others  they  are  scattered  without  apparent  order. 
In  some  cases  they  point  invariably  in  one  direction ;  in  others 
they  may  point  in  any  and  every  direction.  In  rare  instances, 
in  the  Oleander  leaf,  they  are  bunched  together  in  hollows 
)r  depressions  in  the  under  surface  of  the  leaf,  and  do  not  occur 
elsewhere  upon  it. 

(li)  The  epidermis  of  different  species  differs  too  in  the  struc- 
ture of  the  stomata.  In  the  majority  of  cases  the  stomata  con- 
sist, as  in  this  instance,  of  two  crescentic  guard-cells  with  the 
opening  between  them,  but  sometimes  there  are  two  or  more 
superposed  pairs  of  cells ;  rarely  they  form  canals  or  channels 
whose  walls  are  composed  of  several  superposed  circlets  of  cells 
with  several  cells  in  each  circlet. 

(/)  Differences  occur  also  in  the  level  of  the  insertion  of  the 


324  LABORATORY    EXERCISES    IN    BOTANY. 

stomata.  Very  commonly  the  guard-cells  are  on  the  same  level 
as  that  of  the  other  epidermal  cells ;  in  some  species  they  rise  above 
that  level,  and  in  some  other  species  they  are  depressed  more  or 
less  below  it. 

(k)  The  stomata  differ  also  in  different  species  as  respects  their 
relation  to  adjacent  cells.  Sometimes  they  are  scattered  among 
ordinary  epidermal  cells,  but  not  infrequently  the  cells  imme- 
diately surrounding  them  are  more  or  less  modified  in  form  and 
structure,  so  as  evidently  to  be  subsidiary  to  them.  Such  cells  are 
called  "  accessory  cells."  In  one  instance — that  of  Aneimia  frax- 
inifolia — according  to  Strasburger,  the  guard-cells  are  placed  within 
an  ordinary  epidermal  cell  very  much  as  a  picture  within  its  frame. 


\ 


STUDY    OF    EPIDERMAL    TISSUE. 


325 


PLATE  XLIV.,  FIG.  1.— Lower  Epidermis  of  the  Tulip,  view  of  the  exterior  surface. 
The  drawing  was  made  from  a  portion  of  the  tissue  which  had  been  treated  with  potas- 
sium-iodide iodine  (magnification,  285  diameters) :  v,  v,  vacuoles  :  a,  protoplasm  ;  b,  nu- 
cleus :  c,  chloroplast  in  one  of  the  guard-cells  ;  e,  primordial  utricle  shrunken  away  from 
the  cell-wall  by  the  action  of  the  iodine  solution ;  /,  nucleolus ;  g,  cell-wall ;  h,  nucleus 
and  nucleolus  of  guard-cell ;  i,  oil-globule  in  guard-cell. 

FIG.  2. — Small  part  of  Transverse  Section  of  the  Leaf,  showing  a  portion  of  the  lower 
epidermis  and  a  few  of  the  adjacent  parenchyma-cells  :  stomata  are  indicated  at  a  and 
c ;  b,  the  air-chamber  adjacent  to  a  stoma;  d,  nucleus  of  an  ordinary  epidermal  cell ;  e,  a 
vacuole ;  /,  cutinized  exterior  wall ;  g,  thin  radial  wall ;  h,  a  chloroplast  in  one  of  the 
parenchyma-cells ;  i,  nucleus  of  one  of  the  parenchyma-cells.  (Magnification  the  same 
as  in  Figure  1.) 


EXERCISE  VII. 

STUDY  OF    EPIDEKMAL    APPENDAGES. 

THE  following  will  afford  interesting  studies :  young  stems 
and  leaves  of  the  Sycamore  (Platanus  occidentals,  L.)  •  those  of 
the  Hickory  (Gary a  alba,  Nutt.)  •  those  of  the  Nettle  (Urtica 
dioica,  L.) ;  those  of  Shepherdia  (Shepherdia  Canadensis,  Nutt.)  • 
those  of  tobacco  (Nicotiana  Tabacum,  L.) ;  those  of  the  Mullein 
(Verbascum  Thapsus,  L.)  ;  those  of  Mentzelia  (Mentzelia  oligo- 
sperma,  Nutt.,  or  M.  ornata,  Torr.  and  Gray) ;  those  of  the  Horse- 
shoe Geranium  (Pelargonium  zonale,  Willd.)  ;  and  the  hairs  on  the 
filaments  of  the  Spiderwort  (Tradescantia  Virginica,  L.). 

(1)  For  the  first  study  is  selected  a  stem  of  the  Horseshoe 
Geranium  which  is  not  yet  old  enough  for  cork  to  have  begun  to 
form.  Of  this  a  half  dozen  or  more  thin  transverse  sections  are 
made.  Let  one  of  these  sections  be  placed  on  a  slide,  covered  with 
several  drops  of  the  alcannin  solution,  and  set  aside  under  a  bell- 
glass  for  half  an  hour  or  more  to  permit  of  satisfactory  staining. 
Another  of  the  sections  may  be  treated  with  the  chloriodide-of- 
zinc  iodine  and  be  put  away  in  the  same  manner.  A  third  is 
mounted  in  a  drop  of  water  and  focused  upon  with  the  low 
power. 

On  exploring  the  margin  of  the  section  there  will  be  found 
attached  to  the  epidermis  numerous  hairs.  These  hairs  are  not 
all  of  the  same  kind,  for  some  have  a  large  rounded  cell  at  the 
apex,  while  others  are  without  such  a  cell.  The  former  are  the 
glandular  hairs,  the  latter  are  ordinary  simple  ones. 

Let  first  one  of  the  simple  hairs  be  examined.  It  will  be  ob- 
served to  be  long-conical  in  shape,  and  to  be  composed  of  a  vary- 
ing number  of  cells,  usually  three  or  four,  placed  end  to  end. 
The  basal  cell,  more  rounded  and  thicker  than  the  rest,  fits  in 
among  the  other  epidermal  cells,  and  the  apical  cell  is  longer 
than  the  rest  and  terminates  usually  in  a  sharp  point.  The  con- 
tents are  transparent,  though  with  care  there  may  be  discerned, 

327 


328  LABORATORY   EXERCISES   IN    BOTANY. 

even  without  staining,  a  nucleus  and  a  small  amount  of  granular 
protoplasm. 

The  glandular  hairs  are  of  three  different  varieties.  One  variety 
is  much  longer  than  the  rest,  and  consists  usually  of  from  five  to 
seven  cells  arranged  in  a  single  series,  the  apical  cell  constituting 
the  gland,  the  rest  the  stalk.  The  latter  has  its  basal  cell  set  in  the 
epidermis  the  same  as  the  simple  hair  just  described.  The  cells 
above  it  taper  gradually  in  size  until  the  fourth  or  fifth  cell  is 
reached,  when  there  is  an  abrupt  contraction,  the  succeeding  one 
or  two  cells  being  considerably  narrower  and  thinner-walled. 

The  gland-cell  is  nearly  globular,  and  is  so  densely  granular 
that  its  structure  can  only  with  difficulty  be  made  out  without 
the  employment  of  clearing  solutions.  On  the  upper  surface, 
however,  there  is  usually  a  transparent,  highly  refractive  portion, 
the  nature  of  which  will  presently  be  investigated  more  closely. 

Another  kind  of  hair  is  much  shorter,  the  stalk  consisting  of 
only  two  or  three  rather  short  cells,  and  the  gland  consisting  of 
a  very  granular  cell  which  is  usually  oblong  or  ovate  instead  of 
spherical,  and  which  is  often  unsymmetrically  inserted  on  the 
stalk.  The  third  kind  of  hair,  the  most  abundant  of  all,  is  also 
short,  but  with  its  stalk  composed  of  four  or  five  very  short  cells. 
The  gland  is  spherical  like  the  one  first  described. 

It  is  these  glandular  hairs  which  cause  the  clamminess  of  the 
leaves  and  branches,  and  it  is  they  also  which  emit  the  volatile 
essence  that  communicates  to  the  plant  its  peculiar  odor. 

Treating  a  fresh  section  with  potassium-iodide  iodine,  it  is 
found  that  the  cells  of  both  the  simple  and  the  glandular  hairs 
contain  abundant  protoplasm  in  which  may  be  recognized  the 
usual  structure  belonging  to  living  cells — the  nucleus  and  nuele- 
olus,  the  primordial  utricle,  and  the  threads  and  bands  of  pro- 
toplasm. Even  in  the  densely  granular  gland-cells  there  may  in 
some  instances  be  recognized  the  nucleus,  showing  that  they  also, 
in  this  stage  of  growth  at  least,  are  living  cells. 

Besides  the  protoplasm  proper  there  will  also  be  found  a  few 
rounded  or  oval  granules  colored  brown  like  the  protoplasm, 
These  are  leucoplasts,  like  chlorophyll  bodies  except  that  they 
contain  no  chlorophyll. 

To  another  section  are  applied  a  few  drops  of  the  chloral- 
hydrate  solution  for  the  purpose  of  clearing  the  gland-cells,  that 


STUDY    OF    EPIDEKMAL    APPENDAGES.  329 

their  structure'  may  the  better  be  examined.  The  section  should 
be  examined  immediately,  before  the  liquid  has  had  time  com- 
pletely to  disorganize  the  protoplasm.  In  a  few  moments  the 
gland-cell  will  be  sufficiently  clear  to  permit  of  the  nucleus  being 
recognized  easily.  Afterward  the  nucleus  swells,  and  finally,  like 
11  the  other  proteids,  is  rendered  nearly  invisible.  This  clearing 
ikes  the  cell-walls  stand  out  with  beautiful  distinctness,  and 
me  becomes  satisfied  for  the  first  time  that  the  gland  consists 
)f  a  single  cell. 

Let  now  examination  be  made  of 'the  section  which  was  treated 
'ith  the  chloriodide-of-zinc  iodine,  for  the  purpose  of  finding  out 
whether  or  not  the  walls  of  the  hair-cells  are  cutinized.     It  will 
found  that  they  are  stained  the  same  color  as  the  rest  of  the 
epidermis.     The  interior  of  the  walls  may  show  a  bluish  tinge, 
indicating  that  cutinization  is  not  complete,  but  the  exterior  is 
>ngly  cutinized. 

Careful  comparison  of  this  with  the  previous  section  will  render 
it  evident  that  in  those  gland-cells  which  show  at  the  top  a  trans- 
irent  area  the  epidermal  wall  is  divided  into  two  parts,  the  exte- 
-ior  cutinized,  the  interior  not  cutinized  or  but  slightly  so,  and 
that  the  refractive  liquid  lies  between  these  two  portions. 

Sometimes  it  will  be  found,  especially  in  older  glands,  that  the 
cutinized  portion  is  ruptured,  the  wall  therefore  more  or  less  col- 
ipsed,  and  the  refractive  liquid  accumulated  in  droplets  on  the 
)iitside.     Some  of  the  liquid  seems,  in  fact,  to  be  forced  out  by 
internal  pressure  before  the  wall  becomes  ruptured,  as  shown  in 
'igure  2  (PI.  XLIY.).    The  conclusion  naturally  is  reached  that 
the  refractive  liquid,  whatever  it  may  be,  is  secreted  by  the  grau- 
ilar  protoplasm  in  the  gland,  and  is  forced  out  and  accumulates 
between  the  non-cuticularized  and  the  cuticularized  portion  of  the 
wall,  where,  by   reason   of  the  impermeability  of  the   latter,  it 
cumulates   until  the  pressure  becomes  so  great  as  to   force  it 
hrough  or  finally  to  rupture  the  wall. 

Let  now  an  effort  be  made  to  ascertain  the  nature  of  the  refrac- 
tive liquid  secreted  by  the  glands.  On  soaking  one  of  the  sections 
for  twenty  minutes  in  absolute  alcohol,  evidence  will  be  found  that 
the  secretion  has  passed  into  solution.  The  same  result  will  also 
reached  if  another  section  be  treated  for  a  few  minutes  with 
sulphuric  ether.  The  secretion  is,  then,  probably  resinous  or 


330  LABORATORY    EXERCISES    IX    BOTANY. 

oleo-resinous  in  its  nature,  for  fixed  oils  are  with  few  exceptions 
insoluble  in  alcohol.  But  resins  and  fixed  and  volatile  oils  an; 
strongly  colored  by  the  alcannin  solution.  If,  therefore,  either 
of  these  bodies  is  present,  the  section  that  was  treated  with  this 
solution  should  by  this  time  show  a  deep-red  color  in  the  glands. 
An  examination  will  show  that  this  is  a  fact.  The  cutinized  walls 
of  the  hairs  and  epidermis  will  also  be  found  to  be  stained,  though 
less  intensely  than  the  glands,  while  the  rest  of  the  section  is  scarcely 
stained  at  all.  The  conclusion  therefore  is  reached  that  the  contents 
of  the  glands  are  oleo-resiuous. 

Oleo-resins  are  quite  abundant  in  plants,  occurring  often  in 
glandular  hairs,  as  in  this  instance,  but  frequently  also  in  inter- 
nal reservoirs.  Some  of  these  will  be  studied  in  a  future  exercise. 

The  hairs,  especially  the  glandular  ones,  are  probably  chiefly 
protective,  defending  the  younger  and  more  vulnerable  portions 
of  the  plant  against  insect  enemies,  and  sometimes,  by  the  irritant 
character  of  the  secretions,  even  against  the  mammalia. 

(2)  For  the  second  part  of  this  study  are  selected  the  hairs  on 
the  filaments  of  Tradescantia  Virginica. 

In  the  fully-expanded  flower  the  hairs  are  deep-blue  in  color, 
and  look,  under  a  low  power,  much  like  a  minute  string  of  blue 
beads.  But,  beautiful  as  they  are,  they  are  not  sufficiently  trans- 
parent, owing  to  the  highly-colored  sap,  to  permit  the  cell-contents 
to  be  seen  distinctly,  so,  instead,  the  less  highly-colored  hairs  from 
an  unopened  flower-bud  are  selected. 

By  means  of  delicate  forceps  a  few  of  the  hairs  are  carefully 
removed  and  mounted  in  a  drop  of  water,  precaution  being  taken, 
in  putting  on  the  cover-glass,  not  to  crush  or  distort  the  cells. 

On  examining  the  cells  with  the  high  power  a  most  striking 
phenomenon,  a  restless  activity  in  the  contents  of  the  cell,  will 
be  seen.  The  nucleus,  the  nucleolus,  the  primordial  utricle,  and 
the  bands  of  protoplasm  are  visible  as  in  ordinary  cells.  The 
hands  of  protoplasm,  however,  are  not  constant  in  position,  care- 
ful observation  showing  that  they  slowly  shift  their  places  in  the 
cell ;  but  the  most  striking  thing  is  the  rather  rapid  currents 
which  are  seen  in  the  bauds  of  protoplasm  and  in  the  primordial 
utricle,  traceable  by  means  of  the  numerous  fine  granules  (mi<-m- 
somes)  suspended  in  the  transparent  protoplasm.  The  currents 
niav  Ite  seen  running  in  the  endoplasm  up  one  side  of  the  cell  and 


STUDY    OF    EPIDERMAL    APPENDAGES. 


331 


down  the  other,  or  passing  off  into  the  threads  and  bands  that 
connect  the  primordial  utricle  with  the  nucleus.  In  some  of  the 
threads  is  observed  a  single  current  moving  steadily  in  one  direc- 
tion, while  in  others  may  be  seen  two  currents,  side  by  side,  run- 
ling  in  opposite  directions.  The  currents,  however,  are  more  or 

shifting,  as  are  the  bands  themselves. 

This  phenomenon  is  not  exceptional.  It  not  only  occurs  in  the 
lairs  of  many  other  plants,  as  those  of  the  Nettle  and  Glaucium 
luteum,  but  in  the  internodal  cells  and  so-called  leaves  of  the  spe- 
iies  of  Chara  and  Nitella,  in  the  leaves  of  Vallisneria  spiralis,  in 
epidermal  cells  and  hairs  of  the  common  Plantain,  etc.  It  is, 
loreover,  probable  that  the  activity  which  in  these  instances  is  so 
mspicuous  to  the  eye  really  exists  to  a  less  degree  in  the  proto- 
>Iasm  of  all  living  cells. 


STUDY   OF    EPIDERMAL    APPENDAGES. 


333 


PLATE  XLV.— Hairs  from  Stem  of  Pelargonium  zonale  and  from  Filament  of  Trades- 

antia  Virginica : 

FIG.  1.— A  Simple  Hair  of  Pelargonium  :  b,  basal  cell  adjacent  to  ordinary  epidermal 
s;  c,  apical  cell.  Each  cell  contains  protoplasm,  a  nuclexis,  and  a  few  leucoplasts. 

FIG.  2.— One  of  the  Large  Glandular  Hairs  of  Pelargonium :  6,  basal  cell ;  c,  gland- 
ell  containing  densely  granular  protoplasm  ;  d,  oleo-resinous  secretion  between  cuticle 
and  the  rest  of  the  cell-wall ;  e,  exuded  oleo-resinous  matter. 

FIG.  3.— Another  form  of  Glandular  Hair  from  same  plant,  the  gland-cell  of  which  is 
usually  oblong  or  ovate. 

FIG.  4.— A  third  kind  of  Glandular  Hair  from  same  stem. 

(Magnification  of  Figures  1-4,  330  diameters.) 

FIG.  5. — Small  portion  of  Staminal  Hair  from  Tradescantia  Virginica,  showing  currents 
in  the  protoplasm  of  the  cell.  The  arrows  indicate  the  direction  of  the  currents.  (Mag- 
nification about  300  diameters.) 


EXERCISE  VIII. 

STUDY  OF  SUBEROUS  TISSUE  AND  LENTICELS. 

THE  twigs  of  almost  any  woody  gymuosperm  or  dicotyl,  if  of 
sufficent  age,  will  afford  good  examples  for  study.  The  follow- 
ing list  is  one  from  which  the  student  may  make  good  selections : 
the  White  Willow  (Salix  alba,  L.),  the  Oleander  (Nerium  Olean- 
der, L.\  the  Apple  (Pyrus  Malus,  Tourn.),  the  Bittersweet  (So- 
lanum  Dulcamara,  L.\  the  Basswood  (Tilia  Americana,  Z.),-the 
Elder  (Sambucus  Canadensis,  L.\  the  Chestnut  (Castanea  sativa, 
Miller,  var.  Americana,  Gray),  the  Horseshoe  Geranium  (Pelargo- 
nium zonale,  Willd.),  the  Balsam  Poplar  (Populus  balsamifera, 
L.),  the  Locust  (Robinia  Pseudacacia,  L.)9  the  Honey  Locust  (Gle- 
ditschia  triacanthos,  L.),  the  Black  Currant  (Ribes  nigrum,  L.), 
and  the  Sycamore  (Platanus  occidentalis,  L.). 

I.  CORKY  TISSUE. — (1)  The  first  selection  for  this  exercise  is 
le  stem  of  the  Horseshoe  Geranium,  which  was  also  made  the  sub- 
ject of  Exercise  II.,  Part  II.     Especial  attention  is  now  directed 
to  the  corky  tissue.     If  the  stem   be  carefully  observed,  it  will 
be  seen  that  the  upper  portion  is  bright-green  in  color,  that  a 
little  lower  down  the  green  is  giving  place  to  a  brownish  color, 
and  that  still  lower  down  the  green  color  has  quite  disappeared. 
This  is  because  in  the  older  part  opaque  cork  has  been  formed 
just  interior  to  the  epidermis,  obscuring  the  chlorophyll-bearing 
ills  beneath,  while  in  the  younger  portions  this  cork  has  either 

lot  yet  formed  at  all  or  its  cells  are  still  young  and  transparent. 

^u  order  to  understand  the  formation  of  the  cork  it  Avill  be  nec- 
essary to  study  it  in  different  stages  of  development.  Let  study 
first  be  given  to  cork-tissue  which  is  fairly  mature,  by  examining 
sections  of  a  stem  that  is  already  brown  at  the  surface.  The  cross- 
section  will  look  like  that  shown  in  Exercise  II.  (PL  XXXIX.). 
At  the  very  outside  is  the  cork,  the  epidermis  with  its  glandular 
and  other  hairs  having  already  been  pushed  off  by  the  formation 
of  the  cork  beneath  it.  The  latter  may  consist  of  fifteen  or  twenty 

335 


336  LABORATORY    EXERCISES    IN    BOTANY. 

tiers  of  cells  which  are  thin-walled,  four-sided,  considerably 
longer  in  a  direction  parallel  to  the  surface  than  in  the  radial 
direction,  arranged  in  distinct  radial  rows  and  more  or  less  dis- 
tinctly in  tangential  rows  also,  the  arrangement  being  so  compact 
that  no  intercellular  spaces  are  visible.  The  outer  and  older  tiers 
of  cells  are  often  collapsed — that  is,  the  walls  have  fallen  together 
— and  some  of  the  cells  are  scaling  off  at  the  surface :  these  are  the 
oldest  cork-cells,  the  youngest  being  farthest  interior.  It  will  be 
observed  also  that  some  of  the  old  cells  are  opaque  from  containing 
air  and  brownish  coloring  matters.  The  walls  of  the  mature  cells 
are  also  more  opaque  than  those  of  the  younger  ones,  and  the  radial 
walls  are  more  wrinkled  the  older  they  are.  These  appearances 
belong  to  nearly  all  cork-tissue,  and  by  means  of  them  the  tissue 
may  readily  be  recognized. 

If  with  the  cross-section  be  compared  a  longitudinal  one,  it  will 
be  found  that  there  is  little  difference  in  the  appearance  of  the 
cork-tissue,  the  most  noticeable  being  the  slightly  greater  average 
length  of  the  cells  in  longitudinal  view. 

(2)  Let  tests  now  be  applied  to  determine  the  composition  of 
the  cork.  Testing  a  section  with  zinc-chloriodide  iodine,  it  is 
found  that  all  the  older  cork-cells  stain  brown,  while  the  very 
youngest  ones  show  the  cellulose  reaction.  The  mature  cells  are 
then  either  cutinized  or  lignified,  the  choice  being  determined  by 
means  of  another  test :  Preparing  a  new  section  and  putting  it 
on  a  slide,  a  few  drops  of  concentrated  aqueous  solution  of 
chromic  acid  are  applied.  Watching  results  closely,  it  is  seen 
that  after  a  few  minutes  only  the  older  cork-cells  remain,  both 
the  cellulose  and  lignified  tissues  having  been  disintegrated  and 
destroyed.  The  cutinized  epidermis  would  have  behaved  in  the 
same  manner  with  the  same  test,  and  it  is  concluded  therefore 
that  the  cork-cells  are,  chiefly  at  least,  composed  of  cutin.  They 
are  spoken  of  as  suberizcd,  but  cork -substance  or  suberin  is  the 
same  thing  as  cutin.  To  confirm  the  results  obtained  and  to 
make  certain  that  no  mistake  has  been  made,  another  test  is 
applied :  To  a  fresh  section,  on  a  slide,  a  few  drops  of  a  concen- 
trated solution  of  potassium  hydrate  are  applied:  the  cork-cells 
soon  assume  a  yellow  color,  which,  on  warming  the  slide  over  a 
lamp,  becomes  more  decided.  This  is  also  one  of  the  character- 
istic reactions  of  cutinized  and  suberi/ed  tissues. 


STUDY   OF   SUBEROUS   TISSUE   AND    LENTICELS.  337 

But  still  another  test  may  be  tried :  To  a  fresh  section  a  few 
drops  of  cold  Schulze's  maceration  fluid  are  applied,  and  it  will 
soon  be  found  that  the  cork-cells  have  turned  a  yellowish-brown 
color.  The  slide  is  now  heated  over  the  lamp,  and  as  evaporation 
takes  place  fresh  portions  of  the  liquid  are  supplied  by  running  it 
under  the  edges  of  the  cover-glass.  Examining  the  preparation 
from  time  to  time,  it  will  be  found  that  the  other  tissues  gradually 
dissolve  and  disappear,  while  the  cork-tissue  resists  the  action  much 
longer;  but  presently,  if  the  heat  be  continued,  yellow  drops  of  an 
oily-looking  liquid  begin  to  be  formed  in  the  now  swollen  and 
distorted  walls,  and  ooze  out  into  the  cells  and  on  their  surface. 
The  oily-looking  liquid  is  eerie  acid,  soluble  in  alcohol,  ether, 
chloroform,  and  in  dilute  aqueous  solution  of  potassium  hydrate, 
but  not  in  carbon  disulphide.  The  test  most  conclusively  proves 
that  the  walls  are  suberized. 

Cork-cells  also  stain  a  yellowish-green  color  with  methyl-green 
solution,  while  lignified  cells  stain  blue-green,  and  cellulose  ones 
scarcely  at  all ;  cork -cells  do  not  stain  with  hsematoxylin  solution, 
while  both  cellulose  and  lignified  tissues  do ;  but  care  should  be 
taken,  in  applying  this  negative  test,  that  the  sections  are  not 
acid,  and,  if  they  have  been  treated  previously  with  alcohol,  that 
they  have  been  washed  thoroughly  before  applying  the  stain, 
otherwise  cellulose  and  lignified  tissues  may  not  stain,  and  so 
may  be  mistaken  for  cutiuized  tissues. 

(3)  To  study  the  development  of  cork,  sections  must  be  taken 
from  a  younger  portion  of  the  stem.  These  sections  are  made  as 
thin  as  possible,  and  are  cleared  by  treating  them  with  two  or  three 
drops  of  chloral-hydrate  solution  on  a  slide.  In  specimens  of  the 
right  age  will  be  found  on  the  outside  the  epidermis,  consisting 
of  a  single  thickness  of  cells,  having,  as  usual,  the  outer  wall 
thickened  and  cutinized  at  the  surface,  and  beneath  it  the  first 
tier  of  collenchy ma-cells  in  the  process  of  division,  very  thin 
cell-walls  having  been  formed  across  them  in  a  tangential  direc- 
tion. This  is  the  beginning  of  the  cork-formation.  The  outer 
cells  of  the  two  tiers  thus  formed  do  not  again  divide,  but  mature 
into  cork-cells,  while  the  inner  ones  retain  their  activity  and  again 
divide.  Of  the  two  new  tiers  formed  from  one  by  this  last  divis- 
ion, it  is  again  the  outer  tier  that  develops  into  cork,  while  the 
inner  tier  again  undergoes  division,  and  so  the  process  goes  on. 
22 


338  LABORATORY    EXERCISES   IN    BOTANY. 

By  a  judicious  selection  of  different  sections  from  the  same  stem  all 
the  different  stages  of  cork-development  may  be  observed. 

The  inner  layer  of  cells  in  which  the  division  takes  place  is 
called  the  cork  cambium,  or  phellogen. 

It  is  not  the  case  in  all  plants  that  the  cork  begins  to  be  formed 
in  the  layer  of  cells  immediately  beneath  the  epidermis.  In  some 
instances  it  begins  in  the  epidermis  itself;  in  others  a  few  or  sev- 
eral layers  beneath  the  epidermis  ;  and  in  still  others  in  quite  deep- 
lying  tissues.  At  the  close  of  this  exercise  is  given  a  drawing  of 
a  small  portion  of  the  cross-section  of  the  stem  of  the  Bitter- 
sweet, showing  the  cork.  Here  the  formation  began  by  a  divis- 
ion of  the  epidermal  cells,  and  proceeded  interiorly  until,  in  the 
specimen  from  which  the  drawing  was  made,  the  phellogen-layer 
has  become  the  fifth  from  the  surface.  The  cork  is  ordinarily 
formed  centripetally  as  in  the  Geranium,  but  sometimes  ecu //•//'- 
ugaUy  ;  that  is,  the  inner  of  the  two  cells  produced  by  the  divis- 
ion is  the  one  that  develops  into  cork,  while  the  other  remains 
meristematic. 

Cork,  it  will  be  observed,  is,  like  epidermis,  an  admirable  pro- 
tecting tissue.  By  reason  of  its  physical  properties  and  the  ab- 
sence of  intercellular  spaces  it  prevents  excessive  evaporation  from 
the  plant.  It  also,  by  virtue  of  its  impermeability  to  water,  pre- 
vents injury  from  parasitic  organisms.  Bacteria  and  fungi  are  thus 
excluded,  to  a  large  extent  at  least.  It  is  for  these  reasons  that 
the  plant  when  wounded  soon  covers  the  wounded  surface  with  a 
layer  of  cork,  and  even  provides  a  corky  covering  to  the  leaf-scar 
before  the  leaf  separates  from  the  stem. 

II.  LENTICELS. — Attention  has  already  been  drawn  to  lenticels 
in  the  study  of  twigs,  Part  I.  If  there  be  made  several  thin 
sections  transversely  through  the  young  and  still  green  stem  of 
the  Sycamore,  it  will  be  found  that  in  some  instances  the  knife 
has  passed  centrally  through  one  of  these  little  lens-shaped  epi- 
dermal swellings.  If  the  crest  of  the  lenticel  has  not  been  rup- 
tured, there  will  always  be  found  at  this  point  a  stoma,  for  len- 
ticels always  begin  their  formation  immediately  underneath  the 
stoinata.  The  formation  of  lenticels,  in  fact,  precedes  the  forma- 
tion of  cork  under  the  rest  of  the  epidermis  and  initiates  the  latter 
process.  The  cell-division,  when  once  begun,  proceeds  rapidly, 
and  results  in  the  formation  beneath  the  epidermis  of  a  mass  of 


STUDY    OF   SUBEROUS   TISSUE    AND    LENTICELS. 


339 


loosely-arranged  cells  which  press  upon  the  latter,  forcing  it  up- 
ward and  finally  rupturing  it,  and  from  the  opening  thus  pro- 
duced the  spongy  mass  of  cork-cells  protrudes. 

If  the  formation  of  the  leuticel  has  but  just  begun,  there  will 
be  found  only  the  outer  layer  of  collenchyma-cells  in  process  of 

livision  ;  if  well  advanced,  the  whole  of  the  collenchyma  beneath 

le  stoma  will  have  become  involved,  and  the  colleuchyma  as  such 
will  have  disappeared,  the  tissues  of  the  lenticel  having  been  formed 
from  it  by  division  of  its  cells.  Above,  in  the  outer  part  of  the 
lenticel,  are  the  rounded,  loosely-arranged  cells  called  packing  cells, 
and  interior  to  these,  next  the  cortical  parenchyma,  is  a  meristem- 
tissue  or  phellogen  looking  quite  like  the  generative  layer  which 
>roduces  ordinary  cork. 
On  either  side  of  the  leuticel  proper  are  found  the  outer  tiers  of 

)llenchyma-cells  beginning  to  divide  in  planes  parallel  to  the  sur- 
face ;  this  is  the  beginning  of  the  formation  of  cork  under  the  rest 
)f  the  epidermis,  the  formation  proceeding  much  as  that  already 
lescribed  in  the  Geranium. 

The  function  of  a  lenticel  appears  to  be  that  of  supplying  air 
to  the   intercellular  spaces ;  for,  although  the  walls  of  the  cells 
n  mature  are  cutiuized,  the  cells  differ  from  those  of  ordinary 

>rk-tissues  in  having  intercellular  spaces. 


STUDY   OF   SUBEROUS   TISSUE   AND   LENTICELS. 


341 


STUDY   OF   SUBEROUS   TISSUE    AND    LENTICELS.  343 


PLATE  XLVII.,  FIG.  1.— A  few  Cells  from  the  outer  part  of  the  young  Stem  of  Pelar- 
gonium zonale,  showing  the  beginning  of  the  process  of  cork-formation  :  a,  epidermis ; 
&,  collenchyma-cell  immediately  beneath  the  epidermis,  one  of  a  tier  Avhich  has  just 
divided  (the  outer  of  the  two  tiers  is  the  young  cork ;  the  inner,  the  cork  cambium) ;  c 
is  a  glandular  hair.  (Magnification,  340  diameters.) 

FIG.  2.— Transverse  Section  through  Primary  Cork  of  the  Stem  of  Solanum  Dulcamara 
(section  made  in  early  spring,  from  twig  of  previous  year) :  a,  epidermal  cell  converted 
into  cork ;  d,  cork  cambium-cell ;  c,  young  cork-cell ;  d,  older  cork-cell ;  e,  chlorophyll- 
bearing  cell  interior  to  cork  cambium.  (Magnification,  285  diameters.) 


EXERCISE  IX. 
STUDY  OF  WOOD-CELLS  OR  LIBK1FOEM  TISSUE. 

THESE  terms  include  all  those  thick-walled,  fibrous  cells,  not 
tracheary  in  their  nature,  which  occur  in  the  xylem  of  the  vasal 
bundles  of  the  higher  plants,  and  also  the  similar  fibrous  elements 
which  sometimes  occur  outside  of  the  bundles  altogether. 

The  term  "  libriform  "  has  reference  to  the  general  resemblance 
the  fibres  bear  to  the  liber-  or  bast-fibres  often  found  in  the  inner 
bark  of  gymnosperms  and  dicotyls.  The  terms  "  liber-fibres  "  and 

bast-fibres,"  as  commonly  used,  are  stretched  to  embrace  all  those 
fibres  that  occur  in  the  phloem  ends  of  vasal  bundles,  whether  they 
occur  in  the  inner  bark  or  elsewhere  in  the  plant,  and  whether  they 
occur  in  gymuospermous  and  dicotyl  plants  or  in  monocotyls. 

Libriform  fibres  differ  usually  from  liber-fibres  in  being  rela- 
tively less  elongated,  less  tough  and  flexible,  and  less  strongly 
thickened  at  maturity ;  but  there  are  numerous  exceptions,  and 
in  monocotyls  particularly  the  tissues  often  so  completely  merge 
into  one  as  to  be"  wholly  indistinguishable  by  their  structure 
alone.  Some  authors  include  the  two  kinds  of  tissue  under  one 
lead,  and  call  them  svlerenchyma-fibres.  This  mode  of  regarding 
them  is  convenient  if  the  obvious  distinctions  between  the  two 
tissues  as  they  exist  in  their  more  typical  forms  be  not  ignored. 

While  the  writer  cannot  endorse  the  view  that  regards  what 
has  been  called  "sclerotic  parenchyma"  as  more  nearly  related 
to  sclerenchyma-fibres  than  to  parenchyma,  still,  sclerotic  paren- 
chyma and  sclerenchyma-fibres  agree  in  the  fact  that  both  have 
lost  their  cellular  character  and  have  become  purely  mechanical 
tissues.  Moreover,  almost  every  gradation  occurs  between  rounded 
stone-cells  on  the  one  hand  and  bast-fibres  and  wood-cells  on  the 
other :  there  are  elongated  and  pointed  stone-cells,  and  very  short 
and  thick  bast-fibres  that  would  be  difficult  to  distinguish  from 
each  other.  All  of  which  proves  that  the  hard  and  fast  lines 

345 


346  LABORATORY    EXERCISES   IN    BOTANY. 

drawn  in  classifications,  useful  and  even  necessary  as  they  are, 
are  lines  which  do  not  exist  in  Nature. 

Libriform  cells  occur  in  great  abundance  in  the  stems  of  nearly 
all  woody  and  many  herbaceous  dicotyls,  in  the  region  between 
the  pith  and  cambium  zone;  in  the  meditullium  of  most  woody 
roots  of  the  same  group;  and  in  the  stems  and  roots  of  many 
monocotyls  and  pteridophytes.  It  is  unnecessary,  therefore,  to 
point  out  special  examples  for  study. 

The  present  study  is  made  from  the  stem  of  Pelargonium 
zonale,  the  general  structure  of  which  is  already  more  or  less 
familiar. 

(1)  Several  thin  cross-sections  are  first  made  from  a  rather  old 
stem,  and,  after  placing  those  not  required  for  immediate  use  in 
alcohol  for  future  study,  one  of  the  sections  is  laid  on  a  slide 
and  treated  with  a  few  drops  of  the  zinc-chloriodide  iodine, 
covered,  and  examined.  The  wood  which,  along  with  other 
thick- walled  tissues,  forms  a  girdle  about  the  pith  is  found  to  be 
stained  a  decided  brown  by  the  reagent — a  reaction  which,  as 
already  learned,  is  shown  by  lignified  tissues.  As  a  confirmatory 
test  the  phlorogluciu  reagent  is  applied  to  a  fresh  section  and  the 
same  tissues  are  stained  red.  This  liguificatiou  extends  through- 
out the  whole  wall,  but  in  the  chloriodide-staiued  section  the 
middle  lamella  is  a  little  deeper  brown  and  in  the  phloroglucin- 
stained  one  a  considerably  deeper  red,  so  that  this  portion  of  the 
wall  stands  out  with  great  distinctness.  All  of  the  cells  in  this 
region  agree  in  the  lignification  of  their  walls;  but  some  are 
medullary  ray-cells,  others  ducts  or  tracheids,  and  still  others 
are  wood-cells.  The  ducts  may  mostly  be  distinguished  in  their 
transverse  section  by  their  larger  calibre,  but  also,  with  care,  by 
their  markings,  which  may  be  seen  by  focusing  up  and  down. 
The  medullary  rays  may  be  distinguished  by  the  fact  that  they 
occur  in  radial  rows,  are  slightly  elongated  in  a  radial  direc- 
tion, and  are  of  nearly  equal  size,  while  the  wood-cells  average 
smaller  and  are  quite  unequal  in  size  and  irregular  in  their 
arrangement. 

In  outline  the  wood-cells  are  irregularly  many-sided  or  pris- 
matic from  mutual  pressure  during  growth,  and  no  spare-  are 
discernible  between  them. 

The  reason  why  some  cells  appear  much  larger  than  others  is 


STUDY    OF    WOOD-CELLS    OR    LIBRIFORM    TISSUE.  347 

not  because  there  is  really  so  much  difference  in  the  actual  size, 
but  because  they  are  pointed  at  the  ends,  and  splice  over  each  other 
in  such  a  manner  that  in  making  a  cross-section  through  the 
tissue  different  cells  are  cut  at  different  levels — some  through  the 
middle,  others  near  the  ends. 

A  careful  examination  of  the  walls  of  the  cells  under  a  high 
power  and  with  good  illumination  shows  delicate  concentric  strat- 
ification-lines in  the  interior  thickenings,  and  now  and  then  very 
delicate  pore-canals,  though  these  are  by  no  means  so  abundant  as 
in  the  stone-cells  which  were  studied. 

If  cross-sections  of  a  young  stem  be  compared  with  those  of  an 
old  one,  it  will  be  found  that  in  the  former  the  wood- cells  are 
much  less  thickened,  and  in  a  very  young  stem  it  will  be  found 
that  the  cell-walls  are  quite  thin  and  wholly  unliguified. 

(2)  Endeavor  is  now  made  to  learn  more  about  the  cells  by  iso- 
lating them.  This  is  accomplished  by  operating  with  Schulze's 
fluid  on  longitudinal  sections  in  the  manner  directed  in  the  study 
of  stone-cells.  The  relation  of  parts  will  more  satisfactorily  be 
learned  if  the  sections  be  cut  with  considerable  care  to  get  them 
directly  lengthwise  of  the  stem.  They  need  not,  however,  be 
more  than  moderately  thin.  After  treatment  with  the  reagent 
they  should  be  washed  with  care  so  as  not  to  tear  them,  be 
stained  with  methyl-green,  and  then  be  placed  in  a  drop  of  clean 
water  on  a  slide,  and  covered.  The  cover  is  now  gently  tapped 
with  a  needle-point  over  the  centre  of  the  section.  This,  if  not 
carried  too  far,  and  if  the  tissues  have  been  treated  precisely  the 
right  length  of  time  in  the  macerating  fluid,  will  cause  the  fibres 
to  separate  slightly,  and  yet  they  may  be  seen  in  nearly  their  nat- 
ural relations  to  each  other.  It  will  then  be  observed  how  the 
wood-cells  splice  one  over  another  as  has  been  described. 

The  cells  may  now  be  separated  still  farther  and  the  shapes  of 
the  wood-cells  be  studied  more  particularly.  The  fibres  will  be 
found  to  vary  in  length  from  three  or  four  times  as  long  as 
broad  for  the  shortest  ones  to  twenty  or  thirty  times  as  long  as 
broad  for  the  longest  ones,  which  attain  a  length  of  about  one- 
twentieth  of  a  centimetre.  They  mostly  approach  a  fusiform 
shape,  but  the  ends  vary  considerably,  the  cells  sometimes  being 
rather  abruptly  pointed  at  one  or  both  ends  and  sometimes  being 
forked  or  lobed.  The  sides  are  usually  smooth,  but  sometimes, 


348  LABORATORY    EXERCISES    IN    BOTANY. 

where  they  fit  against  a  row  of  medullary  ray-cells,  they  are 
toothed  or  lobed. 

The  walls  have  no  very  conspicuous  marks,  but  with  good 
staining  a  considerable  number  of  oblique  slit-like  pits  may  be 
seen,  more  transparent  than  the  rest  of  the  wall.  If  the  high 
power  of  the  microscope  be  focused  on  one  face  of  the  cell,  the 
slits  will  appear  to  run,  say,  from  the  right  obliquely  upward  to 
the  left,  but  if  it  be  focused  upon  the  opposite  wall  they  will  seem 
to  run  obliquely  upward  from  left  to  right.  One  may  conclude 
from  this  and  other  observations  that  the  markings  are  pits  or 
thin  places  which  lie  along  imaginary  spiral  lines  winding  about 
the  walls,  and  the  possibility  is  suggested  that  the  thickening  de- 
posits have  been  made  spirally  as  in  some  ducts.  This  view 
receives  partial  confirmation  in  the  fact  that  when  the  cells  are 
macerated  until  disintegration  begins,  they  tend  to  separate  into 
fragments  spirally. 

(3)  How  do  the  libriform  cells  of  other  plants  compare  with 
those  of  this  plant?  They  agree,  it  may  be  answered,  in  general 
characteristics,  but  may  differ  in  many  minute  details. 

(a)  They  may  be  much  thicker  walled — in  some  of  the  harder 
woods  so  thick  that  the  lumen  may  almost  be  obliterated.  On 
the  other  hand,  in  many  softer  woods  they  may  be  considerably 
thinner  walled. 

(6)  They  may  differ  in  size  from  those  studied  :  they  may  be 
longer  relative  to  their  thickness,  or  they  may  average  shorter. 
In  these  respects  there  may  be  considerable  variations  within  the 
limits  of  the  same  species. 

(c)  The  markings,  pits,  and  pore-canals  may  be  more  numerous 
and  conspicuous,  or  even  less  so,  but  they  are  never  wholly  absent. 
When  the   markings  are  conspicuous  the  tissue   verges   toward 
tracheary  tissue,  into  which  it  passes  by  insensible  gradations. 

(d)  Sometimes  at  maturity  the  wood-fibre  does  not  repivsi-nt  a 
single  cell,  but  a  row  of  two  or  three  cells  which  have  united  to 
form  the  fibre..     Accordingly,  one  will  occasionally  meet  with  a 
fibre  which  contains  one  or  two  cross-partitions. 


STUDY    OF    WOOD-CELLS    OR    LIBRIFOBM   TISSUE. 


349 


EXERCISE  X. 

STUDY   OF  TRACHEAKY  TISSUES. 

UNDER  this  head  are  included  tracheids  and  ducts.  The  former 
differ  from  wood-cells  in  the  fact  that  their  walls  are  less  evenly 
thickened,  and  this  gives  rise  to  pitted,  spiral,  annular,  ladder- 
like,  or  other  conspicuous  markings.  Commonly  also  their  walls 
are  not  so  strongly  thickened  as  are  the  wood-cells  of  the  same 
plant,  their  calibre  averages  larger,  and  they  are  less  tapering  at 
the  apex,  sometimes  merely  oblique-  or  even  blunt-ended ;  but 
these  differences  are  not  universal. 

The  distinction  between  tracheids  and  ducts  is  simply  this :  in 
the  latter,  two  or  more  cells  situated  end  to  end  have  become 
confluent  by  the  partial  or  total  disappearance  of  the  separating 
partitions,  thus  forming  a  tube  or  vessel  sometimes  of  consider- 
able length.  Ducts  usually  average  somewhat  larger  than  tra- 
cheids in  transverse  diameter,  but  do  not  differ  from  them  in 
their  markings.  Ducts  are,  in  fact,  at  first  thin-walled  cells 
which  in  their  development  pass  through  the  condition  of  tra- 
cheids ;  or  a  row  of  tracheids  may  be  regarded  as  a  duct  arrested 
in  its  development. 

Both  ducts  and  tracheids  occur  in  association  with  wood-cells 
in  the  xylem  of  vasal  bundles.  Tracheary  tissues  have  even  a 
wider  distribution  than  wood-cells,  being  found  in  all  vascular 
plants.  There  are  few  phanerogams  or  pteridophytes  that  do  not 
contain  at  least  two  or  three  different  varieties  of  tracheary  tissue. 

In  the  study  of  the  wood-cells  of  Pelargonium  in  the  last 
exercise  attention  must  have  been  arrested  by  some  of  the  varieties 
of  tracheary  tissue.  Let  the  study  of  the  xylem-tissues  of  this 
plant  now  be  resumed,  especial  attention  being  given  to  the  tra- 
cheary tissues. 

(1)  Among  the  wood-cells  will  be  found  some  cells  having  a 
little  wider  diameter  and  more  numerous,  larger,  and  less  slit- 

351 


352  LABORATORY    EXERCISES    IN    BOTANY. 

like  pits,  but  in  other  respects  similar  to  those  of  which  drawings 
were  made  in  the  last  exercise.  They  are  wood-cells  that  verge 
toward  tracheids. 

(2)  There  will  be  found  other  cells,  with  walls  which  look  like 
an  irregular  network  by  reason  of  the  numerous  large  pits.     In 
these  cells  are  to  be  found  neither  the  remains  of  cross-partitions 
nor  apertures  communicating  with  adjacent  cells.    The  pits  are  not 
in  the  nature  of  apertures,  as  one   might  suppose,  but   are  very 
thin  portions  of  the  cell-membrane.    This  may  be  directly  proved 
by  means  of  the  zinc-chloriodide  iodine  test  or  by  staining  with 
some  diffusive  stain,  as  eosin,  as  was  done  in  the  case  of  the  pits 
in  pitted  parenchyma.    These  cells  are  reticulate  tracheids,  and  are 
in  their  markings  precisely  like  some  of  the  ducts  which  occur 
abundantly  in  the  same  plant  and  associated  with  them.     One  of 
the  tracheids  is  shown  on  Plate  XLIX.  (Fig.  1),  and  beside  it 
(Fig.  2)  a  portion  of  a  reticulate   duct.      Other  kinds  of  tra- 
cheids with  different  markings  may  be  found ;  but,  since  in  their 
markings  tracheids  agree  with  ducts,  the  other  varieties  of  tracheids 
will  be  passed  by,  and  the  remainder  of  this  exercise  will  be  devoted 
to  the  study  of  ducts. 

Several  different  kinds  of  ducts  may  be  found,  but  by  far  the 
most  common  in  the  older  stems  of  this  plant  are  the  reticulate 
ducts. 

(3)  Attention  will  first  be  given  to  these  reticulate  ducts.     The 
treatment  with  the  maceration  fluid  usually  results  not  only  in 
the  separation  of  the  ducts  from  adjacent  tissues,  but  in  the  sep- 
aration of  the  cell-components  of  the  ducts  themselves,  whereby 
may  more  easily  be  observed  the  perforations  in  the  end  partitions 
which  distinguish  the  ducts  from  tracheids.     These  perforations 
are  illustrated  on  Plate    XLIX.    (Figs.  2,  3,  and  Fig.  4,  «). 
In  this  last  the  perforation  is  located  in  the  oblique  end  of  the 
cell.     The  walls  are  usually  more  or  less  prismatic  from  pressure 
against  abutting  cells,  and   it  is  in  the  flat  sides  that  the  thin 
places  or  pits  occur.     These  pits  are  of  the  same  essential  nature 
as  those  already  described  in  parenchyma-  and  wood-cells,  and, 
like  them,  are  means  of  keeping  up  a  lateral  circulation  through 
the  tissues. 

In  some  instances  it  will  be  found  that  the  component  cells  of 
the  ducts  are  blunt-ended,  in  others  that  the  ends  are  oblique, 


I 


STUDY    OF   TRACHEARY    TISSUES.  353 

and  in  still  other?  that  they  are  tapering,  almost  like' wood-cells. 
Considerable  variations  in  this  respect  occur  even  among  the  dif- 
ferent cell-components  of  the  same  duct.  The  terminal  cells  in 
the  series,  however,  are  nearly  always  pointed. 

Associated  with  the  reticulate  ducts  are  found  some  which,  by 
reason  of  the  quite  regularly  arranged  pits  elongated  in  a  trans- 
verse direction,  are  more  properly  called  scalariform  ducts,  so 
named  because  the  markings  appear  somewhat  like  the  rounds 
and  spaces  of  a  ladder.  Between  these  and  the  reticulated  forms 
there  is  every  gradation,  and  sometimes  there  may  be  found  a  cell 
reticulated  on  one  face  and  scalariform  on  another.  Gradations 
also  occur  between  reticulate  and  spiral  ducts,  as  will  presently 
be  seen.  More  especial  attention  will  be  given  to  scalariform 
ducts  in  the  next  exercise. 

(4)  The  next  most  widely  distributed  duct  in  vascular  plants  is 
perhaps  the  spiral.  These  ducts  are  especially  abundant  in  that 
part  of  the  wood  nearest  the  pith.  Their  peculiarity  consists  in 
the  fact  that  the  thickenings  consist  of  one  or  more  spiral  bands 
which  wind,  usually  quite  regularly,  around  on  the  inside  of  the 
cell-wall,  the  rest  of  the  wall  remaining  quite  thin,  and  even  being 
difficult  to  recognize  unless  special  means  are  employed  to  bring 
them  into  view.  The  reason  is  that  the  thin  part  is  of  cellulose, 
which  does  not  stain  with  the  methyl-green.  Often  the  remains 
of  the  transverse  partitions  between  the  component  cells  are  also 
difficult  to  recognize,  especially  as  the  spiral  thickenings  are  con- 
tinuous from  cell  to  cell. 

The  spiral  bands  are  very  readily  pulled  out  of  the  ducts,  and 
in  most  sections  in  which  these  ducts  occur  the  bands  will  be 
found  partially  drawn  out  of  some  of  the  ducts  by  the  section 
knife  in  the  process  of  cutting.  When  the  petiole  of  a  water- 
lily  or  that  of  almost  any  other  petiolate  leaf  of  a  vascular 
aquatic  plant  is  pulled  asunder,  the  spiral  threads  are  pulled  out 
and  may  often  be  seen  with  the  naked  eye,  appearing  like  deli- 
cate cobwebs. 

The  spiral  ducts  in  most  other  species,  as  well  as  in  this,  aver- 
age smaller  in  diameter  than  the  reticulate  and  scalariform  ones. 
They  differ  much  among  themselves,  however,  in  this  respect; 
they  differ  much  also  in  the  number  and  closeness  of  the  spirals. 
In  this  plant  both  double-  and  single-spiraled  forms  are  abundant : 

23 


354  LABORATORY    EXERCISES    IN    BOTANY. 

those  with  a  higher  number  of  spirals  are  rare,  but  in  some  water- 
lilies  as  many  as  eight  have  been  found  in  a  single  duct.  In  some, 
the  spirals,  whether  single  or  double,  are  close,  while  in  others 
they  are  distant.  It  has  just  been  stated  that  connecting  forms 
between  spiral  and  reticulate  ducts  are  sometimes  found.  Illus- 
trations of  this  also  are  found  in  the  Geranium ;  that  is,  in 
some  instances  thickenings  run  across  and  connect  the  neigh- 
boring turns  of  the  spirals,  and  so  form  a  more  or  less  perfect 
network.  If  these  thickenings  are  numerous,  the  spiral  charac- 
ter is  obscured  and  the  duct  acquires  a  decidedly  reticulate  appear- 
ance. Hence  also,  in  searching  through  a  quantity  of  material 
obtained  by  macerating  a  longitudinal  section  in  Schulze's  fluid, 
ducts  will  probably  also  be  found  that  are  distinctly  spiral  at  one 
end  and  reticulate  at  the  other. 

In  some  cases  a  duct  will  at  one  end  contain  a  single  spiral, 
while  at  the  other  there  is  a  double  one ;  or  the  spiral  may  be 
double  in  the  middle  of  the  duct  and  single  at  each  end. 

(5)  There  is  a  close  relation  also  between  spiral  and  annular 
ducts.  In  the  Geranium  the  two  kinds  are  closely  associated  in 
the  layer  of  the  wood  next  to  the  pith.  Annular  ducts  have  all 
the  general  characteristics  of  spiral  ones  except  that  the  thicken- 
ings form  a  series  of  rings  instead  of  spirals,  distributed  along  the 
length  of  the  duct  on  its  interior.  These  rings  are  sometimes  close 
together,  at  others  widely  separated ;  sometimes  they  are  placed 
with  their  plane  at  right  angles  to  the  axis  of  the  duct,  but  often 
obliquely  to  it;  and  they  may  be  at  various  inclinations  in  the 
same  duct.  The  close  relation  between  annular  and  spiral  ducts 
is  shown  by  the  fact  that  a  duct  may  at  one  end  be  annular  and 
at  the  other  spiral.  A  portion  of  a  mixed  duct  of  this  kind  is 
shown  on  Plate  XLIX.  (Fig.  8). 


STUDY   OF   TRACHEAE  Y    TISSUES. 


355 


•*!§ 
S«l 


EXERCISE  XI. 

STUDY  OF  TRACHEAKY  TISSUES  (CONTINUED). 

(1)  The  Scalariform  Duct. — There  was  observed  in  the  study  of 
the  tracheary  tissues  in  the  Geranium  stem  a  form  of  duct  with 
transversely  elongated  pits,  which  duct  was  described  as  scalari- 
forrn.  These  ducts  occur  also  in  many  other  dicotyls.  Typical 
forms,  however,  are  more  readily  found  in  some  monocotyls, 
as  in  the  roots  of  official  Sarsaparilla,  in  Smilax  rotundifolia, 
jL,  and  in  other  species  of  this  genus,  but  especially  in  the 
rhizomes  and  petioles  of  some  ferns,  as  Aspidium  marginale, 
Swartz,  A.  Filix-mas,  Sivartz,  and  Pteris  aquilina,  L.  In  this 
last  plant  particularly  the  ducts  are  beautifully  developed,  and 
they  constitute  by  far  the  larger  proportion  of  the  tracheary  tis- 
sues of  the  plant.  Beautiful  preparations  may  be  made  by  the 
following  process :  Cut  the  sections  quite  thin  and  accurately 
lengthwise  of  the  vasal  bundles.  If  tihe  sections  are  made  from 
fresh  material,  they  should  be  passed  through  alcohol,  trans- 
ferred for  fifteen  or  twenty  minutes  to  a  dilute  aqueous  solution 
of  iodine-green,  rinsed  in  water,  passed  through  ordinary  and 
then  through  absolute  alcohol,  soaked  for  a  few  minutes  in  the 
eosin  oil  of  cloves,  and  mounted  in  xylol  balsam.  By  this  method 
all  the  lignified  portions  of  the  ducts  will  retain  the  green  stain, 
while  the  thin  membrane  of  the  pits  will  have  the  red  color  of 
the  eosin. 

The  ducts,  it  will  be  observed,  are  mostly  prismatic,  with  sev- 
eral or  many  flat  sides  where  they  impinge  against  adjacent  ducts 
or  other  tissues  ;  the  ends  are  either  strongly  oblique  or  taper- 
pointed,  and  where  the  ends  of  two  of  the  component  cells  of  a 
duct  splice  over  one  another  the  ladder-like  thickenings  usually 
remain,  but  the  thin  membrane  between  disappears.  Each  of 
the  flat  sides  of  the  duct,  if  it  impinges  on  another,  is  marked 
with  the  crowded,  transversely-elongated,  and  regularly-arranged 

357 


358  LABORATORY    EXERCISES    IN    BOTANY. 

pits  which  constitute  the  special  characteristic  of  this  form  of 
tracheary  tissue.  Scalariform  ducts  are  usually  of  large  size. 

Beautiful  and  very  instructive  preparations  may  also  be  made 
by  means  of  the  Schulze  maceration  process,  if  after  the  separa- 
tion of  the  component  cells  they  are  stained  by  means  of  iodine- 
green. 

Figure  1  (PL  L.)  shows  a  part  of  one  of  the  ducts  from  the 
rhizome  of  Pteris  aquiliua. 

(2)  The  Pitted  Duct. — This  duct  is  exceedingly  common,  espe- 
cially among  woody  dicotyls,  and  is  often  called  the  dotted  duct. 
It  may  be  studied  to  advantage  in  the  stems  of  any  of  the  follow- 
ing plants :  the  Compass  Plant  (Silphium  laciniatum,  Zr.),  Bitter 
Dock  (Rumex  obtusifolius,  L.\  the  Pumpkin  (Cucurbita  Pepo,  L.\ 
the  Butternut  (Juglans  cinerea,  L.\  the  Walnut  (Juglans  nigra, 
L.\  the  Ailanthus  (Ailanthus  gland ulosus,  Desf.\  the  Oaks,  and 
the  Maples.  Ducts  of  this  kind  are,  like  those  just  described, 
usually  large,  often,  however,  not  very  thick-walled  in  propor- 
tion to  their  diameter,  and  marked  with  numerous  rounded  pits 
which  differ  much  in  size,  number,  and  arrangement  in  different 
plants.  Between  the  typical  forms  with  circular  pits  and  those 
with  pits  transversely  elongated  so  strongly  that  the  ducts  may 
be  called  scalariform  there  is  every  possible  gradation. 

The  very  large  and  complicated  ducts  found  in  the  stem  of  the 
Pumpkin  are  selected  for  study  in  this  exercise.  It  will  be  suf- 
ficient if  thin  longitudinal  and  transverse  sections  be  stained  with 
the  zinc-chloriodide  iodine. 

In  the  transverse  section  the  ducts  appear  as  very  large  circular 
apertures  in  the  xylem  of  the  bundles,  bounded  by  a  rather  thin 
but  distinctly  pitted,  liguified  wall  which  is  backed  by  numerous 
small,  thickish-walled,  and  pitted  parenchyma-cells. 

Under  a  high  power  the  pits  of  the  duct  are  seen  to  be  some- 
what lenticular  spaces  in  the  wall,  with  short  canals  connect  iuir 
them  with  the  interior  and  exterior  faces  of  the  wall.  A  fortu- 
nate staining  of  the  longitudinal  section  with  eosin  or  with  carmine 
would  show  that  the  canals  do  not  extend  clear  through  the  wall, 
but  that  the  pits  are  still  closed  by  a  very  delicate  membrane — 
the  so-called  limiting  membrane — the  persistent  middle  lamella 
of  this  portion  of  the  wall.  They  are  therefore  somewhat  simi- 
lar to,  though  much  smaller  and  more  difficult  to  study  than,  the 


STUDY    OF    TRACHEARY    TISSUES.  359 

bordered  pits  in  the  tracheids  of  gymnosperms,  presently  to  be 
examined. 

In  the  longitudinal  section  are  observed  the  pits  crowded  in 
irregular  groups,  the  groups  bounded  off  from  each  other  by  ele- 
vated unpitted  ridges,  so  that  the  surface  of  the  duct  appears  as 
in  irregular  network  with  numerous  pits  in  the  meshes. 

The  pits  appear  in  this  section  as  rounded  or  oblong  areas,  each 
'ith  a  minute  circle,  more  transparent  than  the  rest,  in  the  centre, 
'he  rounded  shape  of  this  central  thin  portion  of  the  pit  is  rather 
[ceptional  among  dicotyls ;  this  portion  of  the  pit  is  more  com- 
lonly  elongated  and  slit-like  in  form. 

(3)  Let  attention  now  be  given  to  the  tracheids  of  gymno- 
sperms.  Any  species  of  Pine,  Larch,  Fir,  Juniper,  or  Cypress 
will  serve  well  the  purposes  of  study.  In  these  and  most  other 
gymnosperms  ducts  are  rare,  and  so  too  are  wood-cells;  but 
tracheids,  an  intermediate  tissue,  take  the  place  of  both,  and 
constitute  nearly  the  whole  of  the  wood  of  the  plant.  These 
tracheids  have  a  structure  so  peculiar  that  it  is  an  easy  matter  to 
tell  a  gymnospermous  plant  from  any  other  by  a  microscopical 
examination  of  the  wood. 

For  this  study  of  tracheids  is  selected  a  twig  of  the  Bald  Cy- 
press (Taxodium  distichum,  Richard.). 

Sections  are  made  in  three  different  directions  :  (1)  transverse, 
(2)  longitudinal-radial,  and  (3)  longitudinal-tangential.  A  longi- 
tudinal-radial section  is  one  that  passes  lengthwise  of  the  stem 
and  through  the  centre  or  nearly  so ;  that  is,  it  is  cut  in  the 
direction  of,  or  along,  the  medullary  rays.  A  longitudinal-tan- 
gential section  is  one  that  passes  lengthwise  of  the  stem,  but  near 
its  circumference,  and  therefore  crosses  the  direction  of  the  medul- 
lary rays.  It  is  of  course  important  that  both  sections  should 
be  thin  and  be  cut  parallel  to  the  grain.  A  straight-grained  twig 
should  therefore  be  selected  for  sectioning. 

Let  each  of  the  sections  be  treated  with  the  zinc-chloriodide 
iodine,  and  the  longitudinal-radial  section  first  be  examined,  using 
for  the  purpose  the  low  power. 

The  tracheids  will  be  seen  as  elongated  fibres  tapering  usually 
at  each  end,  and  looking,  except  for  their  larger  size  and  peculiar 
markings,  much  like  ordinary  wood-cells.  The  markings  or  bor- 
dered pits,  as  they  are  called,  are  large  compared  with  those  already 


360  LABORATORY    EXERCISES    IN    BOTANY. 

studied,  though  considerably  smaller  than  those  of  many  other 
Conifers.  Each  pit  appears,  in  this  view,  as  a  circle  with  a 
much  smaller  concentric  circle  in  its  interior. 

The  pits  are  in  one  or  two  rows,  but  not  evenly  distributed 
along  the  length  of  the  cells ;  in  some  places  they  are  crowded,  in 
others  widely  separated. 

At  intervals  crossing  the  direction  of  the  tracheids  are  short 
pareuchymatous  cells,  but  with  thickened  and  lignified  walls^ 
These  cells  are  arranged  like  the  bricks  in  a  wall.  The  mass 
constitutes  a  medullary  ray. 

In  order  that  the  nature  of  the  pits  may  be  the  better  under- 
stood, the  longitudinal-tangential  section  is  now  studied.  Here 
are  found  no  markings  on  the  sides  which  are  presented  to  view, 
but  only  on  the  edges ;  that  is,  the  disks  occur  on  the  sides  which 
face  toward  the  medullary  rays,  but  not  on  those  which  face 
toward  the  exterior  or  toward  the  pith. 

Moreover,  in  this  view  the  pits  do  not  appear  round  as  before, 
but  lenticular.  Selecting  a  pit  in  which  the  section  appears  to  have 
passed  through  the  centre,  let  it  be  examined  carefully  with  the 
high  power.  Tt  will  be  found  to  show  a  structure  like  that 
represented  in  Figure  3  (PI.  LI.).  There  is  a  cavity  shaped 
like  a  biconvex  lens  cut  through  the  centre  in  the  direction 
of  the  radii  of  curvature.  At  b,  and  also  opposite  on  the  other 
side  of  the  lens-shaped  area,  are  rounded  apertures.  It  is  one  of 
these  apertures  which,  when  the  disk  is  seen  in  the  radial  section, 
appears  as  the  inner  circle.  At  a  is  the  thin  membrane  which 
divides  the  lenticular  cavity  into  two  parts.  It  is  continuous  with 
the  middle  lamella,  c. 

The  pit,  then,  is  a  lens-shaped  cavity  situated  in  the  common 
wall  between  two  cells,  crossed  through  its  longer  diameter  by  a 
delicate  membrane,  and  perforated  through  its  shorter  diameter 
(except  the  membrane,  which  is  continuous)  by  a  circular  aper- 
ture. 

The  medullary  rays  in  this  view  present  an  appearance  very 
different  from  that  in  the  radial  section,  appearing  as  a  row  of 
from  three  to  five  rounded  cells. 

In  transverse  section  the  pits,  of  course,  look  as  they  do  in  the 
longitudinal-tangential  section.  The  tracheids  in  this  view  ap- 
pear squarish,  and  on  the  radial  face  of  the  walls  are  observed  the 


STUDY    OF    TRACHEA RY    TISSUES. 


361 


pits.  The  medullary  rays  in  this  section  appear  still  different, 
the  cells  being  elongated  and  forming  a  row  which  often  extends 
from  the  pith  to  the  outer  limits  of  the  wood. 

(4)  The  rarest  of  all  forms  of  markings  found  in  tracheids 
and  ducts  is  that  called  the  trabecular.  Its  peculiarity  consists  in 
the  fact  that  the  thickenings,  instead  of  being  on  or  in  the  cell- 
wall,  extend  across  the  lumen  of  the  cell.  These  thickenings,  as 
in  the  other  cases  studied,  are  lignified,  while  the  remainder  of 
the  cell-wall  is  usually  of  cellulose.  Tracheids  of  this  type 
occur  in  the  leaves  of  the  Juniper  and  in  those  of  some  Cycads. 


STUDY   OF   TRACHEARY   TISSUES. 


363 


PLATE  L.,  FIG.  1.— Portion  of  a  Scalariform  Duct  from  the  underground  stem  of 
Pteris  aquilina  (magnification  about  275  diameters). 

FIG.  2.— Transverse  Section  of  large  Pitted  Duct  and  a  few  adjacent  Parenchyma-cells 
from,  the  stem  of  Cucurbita  Pepo  :  &,  lumen  of  the  duct ;  c,  an  adjacent  parenchyma-cell 
with  pitted  walls;  d,  one  of  the  pits;  p,  p,  pits  in  wall  of  duct.  (Magnification  about 
375  diameters.) 

FIG.  3.— Longitudinal  View  of  a  small  portion  of  one  of  the  same  Ducts,  showing  the 
pits  grouped  in  the  meshes  of  a  network  of  ridges,  a,  a.  p  is  one  of  the  pits. 


STUDY    OF   TRACHEARY    TISSUES. 


365 


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EXERCISE   XII. 

STUDY  OF  BAST-FIBRES. 

BAST-  or  liber-fibres  are  found,  as  has  already  been  stated,  in 
e  inner  bark  of  a  very  large  number  of  dicotyls  and  gymno- 
;rms,  but  they  are  absent  from  some,  especially  from  many 
succulent  and  aquatic  species.  They  frequently  occur  also  in  the 
phloem  portion  of  the  leaf-bundles  of  the  same  groups  and  in  the 
phloem  of  the  stems  and  leaves  of  some  monocotyls. 

Convenient  examples  for  the  student  to  investigate  are  the 
stem-barks  of  the  following  plants :  the  Yellow  Cinchona  (Cin- 
chona Calisaya,  Weddelf),  the  Mezereon  (Daphne  Mezereum,  L.), 
the  Yellow  Parilla  (Meuispermum  Canadense,  L.\  the  Slippery 
Elm  (Ulmus  fulva,  Michx.),  the  Elder  (Sambucus  Canadensis, 
L.),  the  Compass  Plant  (Silphium  laciniatum,  L.),  the  Basswood 
(Tilia  Americana,  L.),  the  Umbrella  Tree  (Magnolia  Umbrella, 
Lam.),  the  Bald  Cypress  (Taxodium  distichum,  Richard?),  the 
Tamarack  (Larix  Americana,  Michx.\  and  the  European  Larch 
[Larix  Europea,  DC.). 

(1)  Excellent  examples  of  very  typical  bast-fibres  are  found 
the  stem  of  the  Compass  Plant.  Attention  will  first  be  given 
these.  Having  made  a  few  thin  longitudinal  and  transverse 
sections,  they  may  be  studied  by  aid  of  the  phloroglucin  reagent, 
when  they  will  be  stained  red,  the  middle  lamella  more  distinctly 
than  the  rest ;  or,  better,  they  may  be  studied  by  the  following 
process :  Having  passed  the  sections  through  alcohol,  they  are 
rinsed  in  water  and  are  stained  first  with  a  weak  solution  of 
iodine-green,  in  which  they  are  permitted  to  lie  about  twenty  min- 
utes ;  they  are  again  rinsed  slightly  in  water,  and  transferred  to 
weak,  then  to  stronger,  and  finally  to  absolute  alcohol,  until 
anhydrated  ;  they  are  then  placed  in  the  clove-oil  solution  of 
eosin  and  allowed  to  remain  fifteen  or  twenty  minutes,  and  are 
finally  mounted  in  xylol  balsam. 

367 


368  LABORATORY    EXERCISES    IN    BOTANY. 

Examining  now  one  of  the  transverse  sections,  the  cells  are 
found  to  be  closely  pressed  together  so  that  no  intercellular  spaces 
are  visible.  The  cells  are  observed  to  be  polygonal  in  shape,  much 
like  the  wood -cells  already  studied.  In  size  the  cells  also  appear 
quite  different  from  each  other — a  fact  which  was  observed  in  the 
study  of  wood-cells,  and  one  which  is. susceptible  of  the  same  ex- 
planation— namely,  that  the  section  knife  passed  through  some 
cells  near  the  middle  and  through  others  near  the  attenuated 
ends. 

The  walls  are  not  stained  the  same  color  throughout,  but  three 
distinct  regions  in  them  are  discernible:  the  middle  lamella, 
which  is  deep  green  ;  a  thick  portion  next  interior  to  this,  also 
stained  green,  but  of  a  different  shade,  usually  lighter,  and  which 
is  marked  with  numerous  delicate  concentric  stratification-lines ; 
and,  lastly,  a  much  thinner  interior  portion,  not  green  at  all,  but 
red  or  reddish  from  having  taken  up  the  eosin  stain,  while  the 
green  was  either  not  retained  or  was  retained  to  but  a  slight 
extent.  This  portion,  therefore,  is  not  yet  liguified,  but  is  com- 
posed of  cellulose  chiefly  ;  it  is  manifestly  the  youngest  portion  of 
the  thickened  wall. 

Careful  focusing  with  the  high  power  will  also  show  delicate 
straight  tubes  running  from  the  lumen  of  one  cell  to  that  of 
another,  interrupted,  however,  by  the  middle  lamella.  These 
tubes  are  the  already  familiar  pore-canals. 

Turning  now  to  the  longitudinal  section,  the  fibres  are  here 
seen  to  be  put  together  much  as  wood-cells,  splicing  one  over 
the  other  by  their  attenuated  ends,  and  forming  a  very  tough 
and  strong  tissue.  In  shape  they  resemble  wood-cells,  but 
they  are  relatively  somewhat  longer  and  thicker-walled.  Their 
length  will  be  found  to  be  as  many  as  forty  or  fifty  times  their 
thickness.  The  fibres  do  not  all  represent  single  cells.  In  some 
cross-partitions  may  be  seen,  showing  that  a  fibre  is  occasionally 
at  least  the  product  of  two  or  more  cells. 

With  care,  if  the  section  is  thin,  the  pore-canals  and  stratifica- 
tion-lines may  be  seen  ;  but  here  the  former  often  look  like  dots 
instead  of  lines  or  tubes,  for  reasons  already  explained  in  the 
study  of  stone-cells. 

It  would  also  be  found  profitable  to  remove  the  bark  from  a 
part  of  the  stem  and  to  isolate  the  fibres  by  means  of  Schulzc's 


STUDY    OF    BAST-FIBRES.  369 

fluid,  staining  them  afterward  with  iodine-green.  The  transverse 
partitions  will  thus  the  better  be  seen,  and  perhaps  also  some 
fibres  will  be  found  that  are  somewhat  branching  or  forked  at 
their  ends. 

(2)  For  branching  fibres,  however,  the  inner  bark  of  the  Euro- 
pean Larch  is  more  favorable  for  study. 

Longitudinal  sections  of  the  bark  are  made  and  are  treated  with 
Schulze's  maceration  fluid  ;  after  washing,  the  tissues  are  teased 
apart  with  needles,  are  stained  with  the  solution  of  methyl- 
green  or  with  that  of  iodine-green,  and  are  then  examined.  The 
fibres  are  found  to  be  relatively  shorter  than  those  of  the  Com- 
pass Plant — many  of  them  so  short  as  closely  to  resemble  stone- 
cells  in  appearance ;  most  of  them  have  the  walls  so  excessively 
thickened  that  in  places  the  lumen  is  wholly  obliterated ;  and 
while  the  majority  of  the  fibres  are  fusiform  in  shape  and  un- 
brauching,  a  considerable  number  may  be  found  that  are  vari- 
ously lobed,  forked,  or  branched.  An  occasional  fibre  will  also 
be  found  that  has  a  relatively  large  lumen  or  whose  wall  is 
but  little  thickened.  In  other  respects  there  will  be  found 
but  little  difference  between  branching  fibres  and  those  already 
studied. 

In  the  typical  bast-fibre  the  lignification  of  the  wall  is  not 
nearly  so  strong  as  that  of  the  wood-cell  or  that  of  the  tra- 
cheid  or  duct,  though  the  thickening  is  usually  excessive.  In 
many  cases,  therefore,  the  coloration  by  means  of  the  phloroglu- 
cin  reagent  is  but  slight,  or  even  in  some  instances  there  is  no 
color  at  all.  This  is  particularly  true  of  the  long  and  tough 
fibres,  such  as  those  in  Flax  and  Hemp,  that  are  so  extensively 
employed  in  the  production  of  textile  fabrics.  Perhaps  the  fact 
of  their  being  but  slightly  lignified  accounts  for  their  flexibility 
and  tenacity.  Very  strongly  lignified  fibres,  at  any  rate,  are  apt 
to  be  harsh  and  brittle. 

(3)  At  the  other  extreme  from  the  fibres  of  Flax  and  Hemp,  so 
far  as  their  structure  is  concerned,  are  the  very  short  and  thick 
fibres  of  the  Cinchonas. 

To  study  these  a  fragment  of  the  bark  of  Cinchona  Calisaya 
may  be  soaked  in  water  for  twenty-four  hours  and  then  be  sec- 
tioned, a  series  of  both  longitudinal  and  transverse  sections  being 
made.  The  latter  are  bleached  by  soaking  them  in  Labarraque's 

24 


370  LABORATORY    EXERCISES    IN    BOTANY. 

solution  until  the  brown  color  disappears ;  they  are  then  washed 
thoroughly  in  water  to  get  rid  of  the  last  traces  of  the  bleach  inn; 
solution,  and  are  stained  with  iodine-green.  The  bast-fibres 
occur  either  as  isolated  cells  or  as  clusters  of  two  or  three  scat- 
tered without  much  regularity  through  the  inner  bark.  They 
are  excessively  thickened  and  strongly  lignified,  the  lumen  being 
in  many  instances  almost  obliterated.  They  are  also  of  large 
diameter  for  bast-fibres.  The  thick  walls  usually  show  three 
distinct  strata,  each  of  which  is  subdivided  into  numerous  delicate 
lamellae.  The  pore-canals  also,  though  not  very  numerous,  are 
quite  distinct. 

If  the  microscope  is  provided  with  a  polariscope,  there  will  be 
found  here  an  excellent  illustration  of  the  fact  that  thickened 
cell-walls  often  beautifully  polarize  the  light  which  passes 
through  them,  so  that  when  the  Nicol  prisms  of  the  polarizer 
are  crossed  the  fibres  show  brilliant  color-effects.  These  effects 
are  due  to  a  difference  of  tension  in  the  different  lamella?  com- 
posing the  cell- wall. 

The  longitudinal  sections  of  Cinchona  are  treated  in  the  usual 
way  with  Schulze's  fluid  to  isolate  the  fibres.  It  will  be  found 
on  staining  and  examining  them  that  for  bast-fibres  they  are 
excessively  short,  their  length  averaging  perhaps  not  more  than 
five  or  six  times  their  thickness,  and  in  some  cases  even  they 
might  easily  be  mistaken  for  stone-cells.  They  are  acute,  rounded, 
or  wedge-shaped  at  the  ends,  seldom  or  never  lobed  or  branch  ing, 
and  harsh  and  brittle  rather  than  tough.  If  the  bast-fibres  of 
different  plants  were  arranged  to  form  a  scale,  with  the  shortest 
and  thickest  at  one  end  and  the  longest  and  most  flexible  at  the 
other,  at  or  near  the  former  extreme  would  be  found  the  fibres 
of  the  Cinchonas;  at  the  latter,  those  of  Mezereum  and  Flax  ; 
while  those  of  the  Compass  Plant  would  be  found  somewhere 
near  the  middle. 

Indistinguishable  in  form  and  structure  from  bast-fibres  arc 
many  of  the  sclerenchyma-fibres  found  altogether  outside  of 
vasal  bundles,  such,  for  example,  as  the  strengthening  fibres 
beneath  the  epidermis  in  some  leaves,  and  the  fibres  which  occa- 
sionally occur  in  the  fundamental  tissues  of  the  cortex  in  many 
vascular  cryptogams  and  in  some  flowering  plants.  Associated 
with  bast-fibres  are  often  found  elongated,  thick-walled,  blunt-  or 


STUDY   OF    BAST-FIBRES. 


371 


square-ended  cells  that  differ  from  the  bast-fibres  only  in  their 
shape.  They  are  sometimes  called  rod-  or  staff-cells.  With 
these  are  also  frequently  associated  ordinary  stone-cells,  and  be- 
tween the  latter  and  the  fonner  may  occur  every  possible  gra- 
dation. 


STUDY   OF   BAST-FIBRES. 


373 


a 


PLATE  LIL,  FIG.  1.— Transverse  Section  of  a  few  Bast-fibres  from  the  inner  bark  of 
Silphium  laciniatum  (magnified  830  diameters) :  a,  inner  unlignified  or  only  partially 
lignified  portion  of  thickened  wall ;  b,  middle  lamella  ;  c,  middle  portion  of  wall ;  d,  lu- 
men ;  e,  pore-canal. 

FIG.  2.— Longitudinal  Section  of  Bast-fibres  of  Silphium  laciniatum  (magnified  830 
diameters).  The  letters  a,  b,  c,  d,  and  e  refer  to  the  same  things  as  in  the  transverse  sec- 
tion ;  p,  pt  p,  adjacent  parenchyma-cells. 


STUDY    OF   BAST-FIBRES. 


375 


PLATE  LIIL— Secondary  Bast-fibres  from  the  inner  bark  of  Larix  Europeea  (magnified 
about  80  diameters) :  a,  b,  c,  branching  fibres,  the  last  approaching  a  stone-cell  in  form ; 
d,  an  exceptional  fibre  with  a  relatively  large  lumen.  The  fibres  from  which  the  draw- 
ings were  made  were  isolated  by  means  of  Schulze's  fluid. 


STUDY   OF    BAST-FIBEES. 


377 


PLATE  LTV.,  FIG.  1.— Transverse  Section  of  a  cluster  of  three  Bast-fibres  from  the  inner 
bark  of  Cinchona  Calisaya,  showing  strata,  lamellae,  and  pore-canals.  (Magnified  340 
diameters.) 

FIG.  2.— View  of  a  Bast-fibre  from  the  same  bark,  isolated  by  means  of  Schulze's  fluid 
(the  fibre  is  rather  longer  than  the  average):  a,  the  narrow  lumen;  6,  one  of  the  pore- 
canals.  (Magnification,  210  diameters.) 


EXERCISE  XIII. 

STUDY  OF  SIEVE-TISSUE. 

SIEVE-TISSUE  occurs  in  the  phloem  of  vasal  bundles,  very 
rarely  elsewhere  in  the  plant.  It  constitutes  the  most  character- 
istic tissue  of  the  phloem,  and  it  is  nearly  always  associated  with 
narrower,  elongated  parenchyma-cells  called  "companion-cells." 
Sieve-cells  are  almost  always  considerably  elongated  in  the  direc- 
tion of  the  length  of  the  vasal  bundles  in  which  they  occur ;  their 
walls  are  thin  and  unlignified,  but  possess  in  certain  parts,  usually 
in  the  end  partitions,  more  or  less  thickened  plates  with  numerous 
minute  sieve-like  perforations  through  which  proteids  and  other 
colloids  in  the  semi-liquid  form  may  circulate  from  cell  to  cell  of 
the  tissue. 

The  tissue  in  most  plants,  owing  to  the  small  diameter  and  thin 
walls  of  the  cells  and  the  minuteness  of  the  perforations  in  the 
plates,  is  not  an  easy  one  to  study,  but  favorable  examples  are 
the  following :  the  stems  of  the  Pumpkin  (Cucurbita  Pepo,  L.)t 
the  Squash  (Cucurbita  maxima,  Duchesne),  the  Watermelon  (Ci- 
trullus  vulgaris,  Schrader),  and  the  Hop  (Humulus  Lupulus, 
L.) ;  the  petiole  of  the  Grape  (any  of  the  commonly  cultivated 
species) ;  the  inner  bark  of  the  Slippery  Elm  (Ulmus  fulva, 
Michx.)  and  the  Basswood  (Tilia  Americana,  L.) ;  and  the  rhi- 
zome of  the  Mayapple  (Podophyllum  peltatum,  L.). 

The  sieve-tissue  of  the  Pumpkin  will  be  studied  in  this  exercise, 
and  the  preference  is  given  to  material  which  has  been  preserved 
in  alcohol.  Several  sections,  both  longitudinal  and  transverse, 
are  made,  taking  care  that  the  former  pass  lengthwise  of  one  of 
the  vasal  bundles  in  a  radial  direction,  or  at  least  through  the 
phloem  portions  of  a  bundle.  Several  sections  may  have  to  be 
rejected  before  one  is  found  that  will  show  the  tissue  to  the  best 
advantage. 

(1)  Treat  one  of  the  transverse  sections  with  the  phloroglucin 
reagent,  cover  it,  and  examine  it  with  the  low  power.  It  will  be 

379 


380  LABORATORY    EXERCISES    IN    BOTANY. 

observed  that  there  are  tea  vasal  bundles  arranged  in  two  circles 
about  the  central  hollow  in  the  stem.  Each  of  the  bundles  con- 
sists of  a  xylem  mass  containing  several  large  ducts  as  well  as 
many  smaller  ones,  which  are  stained  red  by  the  reagent,  and 
two  masses  of  phloem  which  are  wholly  unstained,  one  facing 
outward  or  away  from  the  central  hollow,  the  other  toward  it. 
The  bundles  of  the  inner  circle  are  the  larger,  and  are  usually  the 
more  favorable  for  study. 

Having  brought  a  phloem  part  of  one  of  these  bundles  to  the 
centre  of  the  field  of  the  microscope,  the  high  power  is  turned  on 
and  the  structure  is  examined.  The  phloem  will  be  found  to  be 
composed  mainly  of  two  kinds  of  cells,  one  kind  rather  large,  the 
other  much  smaller,  and  all  without  visible  intercellular  spaces. 
The  larger  cells  are  the  sieve-tubes  ;  the  smaller  cells  are  the  com- 
panion-cells or  other  intermixed  parenchyma-cells.  Many  of  the 
sieve-cells  appear  empty  because  the  cells  are  long  and  the  section 
has  passed  between  the  sieve-plates,  which  in  this  case  are  in  the 
end  partitions  of  the  cells  ;  but  in  some  cells  will  be  observed  the 
plates,  and  unless  they  are  placed  too  obliquely  to  the  plane  of 
vision  there  will  be  seen  the  numerous  delicate  apertures  in 
them.  These  apertures  may  be  empty,  or  they  may  be  par- 
tially, or  sometimes  completely,  filled  with  albuminous  matters 
and  a  peculiar  thickening  substance  called  callose,  so  that  they 
appear  darker  than  the  adjacent  wall-substance. 

If  one  of  the  sections  be  stained  with  strong  potassium-iodide 
iodine,  there  will  be  found  plates  whose  meshes  are  deep-brown 
from  the  proteids  they  contain,  while  the  cellulose  wall-substance 
is  unchanged  in  color.  The  companion-cells  are  seen  to  be  very 
rich  in  proteid  matters. 

(2)  Let  now  a  longitudinal  section  which  has  been  treated  for 
a  few  minutes  with  eosin  solution  be  studied.  This  solution 
stains  the  proteid  contents  of  the  sieve-tubes  strongly,  and  so 
enables  one  to  identify  the  tissue.  These  proteids  will  have 
been  shrunken  by  the  action  of  the  alcohol,  so  that  they  do  not 
nearly  fill  the  sieve-tube  except  in  the  vicinity  of  the  plate,  where 
they  are  usually  denser  and  more  abundant.  Here,  however,  it 
will  often  be  found  that  the  shrinking  effect  of  the  alcohol  has 
drawn  the  mass  slightly  away  from  the  plate,  pulling  out  more 
or  less,  so  that  they  may  be  seen  distinctly,  the  line  threads  of 


STUDY   OF   SIEVE-TISSUE.  381 

albuminous  matter  that  penetrate  its  meshes  and  connect  it  with 
that  of  the  next  cell. 

The  companion-cells,  though  elongated,  are  much  shorter  than 
the  sieve-cells,  their  ends  are  square  or  oblique,  and  their  proto- 
plasm is  nucleated.  In  the  common  wall  between  these  cells  and 
the  sieve-tubes  will  be  found  minute  pits,  but  no  perforations. 

Now  let  there  be  examined  a  longitudinal  section  that  has  been 
treated  for  twenty  minutes  or  more  with  a  weak  watery  solution 
of  anilin-blue,  and  mounted  either  in  glycerin  or  in  the  chloral- 
hydrate  solution.  If  mounted  in  glycerin,  the  best  staining  re- 
sults will  be  obtained  if  the  section  be  allowed  to  remain  an  hour 
or  more  in  the  glycerin  before  examining  it.  Most  of  the  color 
will  then  have  disappeared  from  the  cell-walls,  but  will  remain  in 
the  protoplasm  and  nuclei  of  the  companion-cells  and  in  the  albu- 
minous matters  of  the  sieve-tubes,  and  the  deposits  of  callose  in 
the  pores  and  on  the  surface  of  some  of  the  sieve-plates  will  be 
stained  a  fine  blue  color  somewhat  different  in  tone  from  the  rest, 
so  that  they  may  readily  be  recognized. 

If  desired,  satisfactory  permanent  mounts  may  be  made  by 
carrying  the  sections,  after  staining,  through  weak  into  strong 
glycerin,  and  finally  enclosing  them  in  glycerin  gelatin. 

Another  method  which  yields  good  results  is  as  follows :  Wash 
out  the  glycerin  with  water,  anhydrate  by  passing  the  sections  suc- 
cessively through  weak,  strong,  and  absolute  alcohol,  then  through 
oil  of  cloves  tinted  with  eosiu,  and  finally  mount  in  xylol  balsam. 
By  this  means  the  slimy  albuminous  matter  in  contact  with  the 
sieve-plate  acquires  a  tint  different  from  that  of  the  callus,  ren- 
dering it  easier  to  distinguish  the  one  from  the  other. 

Satisfactory  but  more  fugitive  results  are  obtained  by  means  of 
the  anilin-blue  and  the  chloral-hydrate  solution.  After  staining 
with  the  blue  the  sections  are  mounted  in  the  chloral-hydrate 
solution.  The  color  very  rapidly  disappears  from  the  cell-walls, 
but  rather  slowly  from  the  other  parts;  at  the  same  time  the 
swelling  of  the  walls  and  the  clearing  which  the  solution  pro- 
duces are  of  advantage  in  studying  the  structure. 

Sieve- tissues  appear  to  be  an  important  means  of  transferring 
proteid  nutriment  from  one  part  of  the  plant  to  another.  The 
slimy,  albuminous  matters  in  the  interior  of  the  tubes  do  not 
appear  to  be  protoplasm,  but  to  be  other  proteinaceous  material 


382  LABORATORY    KXKUCISES    IN    JJOTANY. 

in  the  process  of  transfer.  The  sieve-cells,  however,  are  probably 
still  living  cells,  for  it  has  been  found  that  the  wall  is  lined  with 
a  delicate  layer  of  protoplasm,  but  a  nucleus  has  not  been  discov- 
ered in  them. 

The  callose  of  sieve-tubes  is  something  related  to,  but  some- 
what different  from,  cellulose.  That  it  is  not  identical  with  cellu- 
lose is  evident  not  only  from  the  fact  that  it  stains  much  more 
strongly  with  anilin-blue  and  corallin,  but  also  from  the  fact  that 
it  is  wholly  soluble  in  1  per  cent,  potassium-hydrate  solution, 
while  cellulose  is  not. 

Callose  is  not  confined  to  sieve-tubes,  but  occurs  in  the  hyphu? 
of  some  fungi,  in  certain  pollen-grains,  in  the  seeds  of  certain 
of  the  Borraginacese,  and  associated  with  calcium  carbonate  iu 
cystoliths  and  in  certain  encrusted  cell-walls. 


o 


STUDY   OF   SIEVE-TISSUE. 


383 


PLATE  LV.,  FIG.  1.— Transverse  Section  of  Pumpkin  stem  (magnified  about  5  diam- 
eters) :  a,  sclerenchymatous  ring  in  cortex  ;  6,  one  of  the  outer  circle  of  vasal  bundles ; 
c,  one  of  the  inner  circle  of  bundles ;  d,  central  pentagonal  hollow. 

FIG.  2.— Transverse  Section  of  a  portion  of  the  Soft  Bast  of  Pumpkin  stem  (magnified 
210  diameters) :  a,  a,  companion-cells ;  b,  sieve-plate  of  sieve-tube ;  c,  c,  sieve-tubes  cut 
through  between  the  plates  so  that  the  latter  are  not  shown. 


STUDY    OF   SIEVE-TISSUE. 


385 


PLATE    LVI—  Longitudinal  Section  of  the  Soft  Bast  of  Pumpkin  stem  (magnified  210 
diameters) :    a,  nucleus  of  companion-cell ;  b,  b,  sieve-plates  ;   e,  albuminous  matter 
shrunken  away  from  plate  by  action  of  alcohol ;  d,  pit  in  lateral  wall  of  sieve-tube  ;  e, 
thin  layer  of  protoplasm  lining  sieve-tube. 
25 


EXERCISE  XIV. 

^ 
STUDY  OF   LATICIFEKOUS  TISSUE. 

THERE  are  two  principal  kinds  of  milk-  or  laticiferous  tissue 
—the  simple,  and  the  complex  or  articulated.  For  the  study  of 
the  former  kind  selections  may  be  made  from  the  following  objects  : 
the  stem  of  the  common  greenhouse  plant  Euphorbia  spleudens ; 
the  root  of  the  Flowering  Spurge  (Euphorbia  corollata,  L.} ;  the 
stem  and  root  of  the  Common  Milkweed  (Asclepias  cornuti, 
Zteca/sne) ;  the  stem  and  root  of  the  Purple  Milkweed  (As- 
clepias purpurasceus,  L.)-  the  stem  and  root  of  the  Dogbane 
(Apocynum  androsaemifofium,  Z.);  the  stem  and  root  of  the 
Canadian  Hemp  (Apocynum  canuabinum,  L.)',  the  stem  of  the 
Fig  (Ficus  Carica,  L.) ;  and  the  stem  of  the  Oleander  (Nerium 
Oleander,  L.). 

For  the  study  of  complex  laticiferous  tissues  selections  from 
the  following  objects  may  be  made  :  the  root  of  Dandelion  (Ta- 
raxacum officinale,  Weber) ;  the  root  of  Chicory  (Cichorium  In- 
tyburi,  L.) ;  the  stems  of  AVild  Lettuce  (Lactuca  Scariola,  L.,  and 
L.  Canadeusis,  L.) ;  the  stem  and  root  of  Celandine  (Chelido- 
nium  majus,  L.) ;  the  stem  and  young  capsule  of  the  Opium 
Poppy  (Papaver  somniferum,  i.);  the  root  of  Spanish  Salsify 
(Scorzonera  hispanica,  L.);  and  the  root  of  Common  Salsify 
(Tragopogon  porrifolius,  L.). 

I. — For  the  study  of  simple  laticiferous  tissue  there  is  selected 
from  the  former  list  the  stem  of  the  common  Milkweed. 

In  the  study  of  laticiferous  tissue  of  any  kind  the  parts  of  the 
living  plant  to  be  investigated  should  be  cut  into  pieces,  not  too 
small,  and  immediately  be  dropped  into  strong  alcohol  and  there 
allowed  to  remain  until  the  liquid  has  thoroughly  penetrated  the 
structure.  The  object  of  this  treatment  is  to  coagulate  the  latex 
before  it  has  had  time  to  escape  from  the  vessels,  so  that  the  course 
of  the  latter  may  the  more  readily  be  traced. 

Having  thus  prepared  the  material,  thin  transverse  and  longi- 

387 


388  LABORATORY    EXERCISES    IN    BOTANY. 

tudinal  sections  are  made  and  stained,  some  of  them  by  means  of 
the  iodine-green  solution.     To  one  or  two  of  the  remain  in- 
tious  of  each    kind  are  added  a  few  drops  of  zinc-chloriodide 
iodine,  and  they  are  set  aside  for  a  while  until  the  cellulose  walls 
have  acquired  the  blue  color. 

Placing  one  of  the  green-stained  transverse  sections  under  the 
microscope  and  examining  it  with  the  low  power,  the  milk-tube.s 
may  be  seen  in  abundance  in  the  pith  and  in  the  middle  and 
inner  bark.  In  the  pith  and  in  the  middle  bark  they  mav 
readily  be  recognized  by  the  fact  that  they  are  narrower  than 
the  adjacent  parenchyma-cells,  by  their  more  densely  granular 
contents,  and  by  the  absence  of  a  nucleus.  It  will  also  often  be 
found  that  their  walls  are  somewhat  thicker  than  those  of  the 
parenchyma-cells,  particularly  if  the  section  be  that  of  a  well- 
matured  stem.  This  difference  will  be  noticeable  particularly  in 
the  pith  and  soft  bast  if  to  an  unstained  section  a  few  drops  of 
chloral-hydrate  solution  be  applied. 

Moreover,  the  razor  in  passing  through  the  tissue  frequently 
draws  the  elastic  and  extensible  masses  of  latex  more  or  less  out 
from  the  tubes,  thus  aiding  in  the  identification  of  the  tissue. 
The  latex  appears  opaque  and  densely  granular  as  viewed  by 
transmitted  light. 

Turning  now  to  one  of  the  green-stained  longitudinal  sections, 
and  having  identified  the  laticiferous  tubes  with  the  low  power, 
let  them  be  studied  minutely  with  a  higher  one. 

There  will  be  but  little  difficulty  in  tracing  the  tissue  by  aid 
of  the  coagulated  latex  for  considerable  distances  through  the 
stern,  for  the  latex-cells  form  tubes  of  indefinite  length.  While 
their  general  course  is  lengthwise  of  the  stem,  they  are  neverthe- 
less somewhat  wavy  or  serpentine,  though  less  so  in  this  species 
than  is  often  the  case  in  other  plants.  The  tubes  do  not  branch 
freely,  although  they  do  so  occasionally,  and  very  rarely  are  the 
branches  of  one  tube  observed  to  anastomose  with  those  of  an 
adjacent  one. 

For  these  reasons,  and  because  the  tube  with  its  branches  i< 
believed  to  represent  a  single  cell,  even  though  it  may  run  the 
entire  length  of  the  plant,  this  variety  is  called  "simple  laticif- 
enms"  tissue.  Wherever  it  occurs  its  structural  features  are 
essentially  similar  to  those  observed  in  this  plant. 


STUDY    OF    LATICIFEROUS   TISSUE.  389 

Removing  this  section  now,  and  substituting  for  it  a  set  of 
sections  which  have  been  treated  with  the  ziuc-chloriodide  iodine, 
it  will  be  found  from  the  blue  stain  that  the  walls  of  the  tubes 
are  of  cellulose. 

From  the  brown  color  which  the  iodine  has  communicated  to 
the  latex  it  is  also  concluded  that  the  latter  contains  proteid  mat- 
>rs.     Starch   is   not  found   in  the  latex  of  this  plant  either  by 
leans   of   this   test   or  by  that  of   the  chloral-hydrate  iodine, 
lough  it  occurs  in  the  latex  of  some  other  plants — for  example, 
in  that  of  Euphorbia  splendens,  where  the  grains  are  rod-like, 
clavate,  or  dumb-bell-shaped. 

That  the  latex  contains  oily  or  oleo-resinous  matters  is  suf- 
ficently  evidenced  by  the  fact  that  it  stains  deep-red  with  the 
alcannin  solution.  It  is  the  presence  of  these  matters,  emulsified 
by  aid  of  the  albuminous  and  mucilaginous  substances  also  present, 
that  gives  to  the  fluid  its  milky  appearance. 

The  last  test  applied  also  reveals  the  presence  in  the  latex  of 
other  bodies — solid  angular  particles,  often  of  considerable  size, 
which  do  not  take  up  the  stain.  On  testing  them  with  potassium- 
hydrate  solution  they  remain  unaffected,  as  they  do  also  when 
treated  with  acetic  acid  ;  but  on  testing  them  with  hydrochloric 
acid  they  disappear  without  effervescence.  It  is  concluded,  there- 
fore, that  they  are  composed  of  calcium  oxalate.  They  do  not 
appear  to  be  present  in  all  of  the  latex-tubes,  though  they  are 
rather  abundant  in  some. 

II. — Complex  laticiferous  tissue  will  now  be  studied  as  it  is 
)und  in  the  root  of  the  Common  Dandelion.  The  peculiar  dis- 
•ibution  of  the  milk-tissue  in  the  cortex  has  already  been  observed 
the  study  given  to  this  root  in  Part.  I. 

Several    sections,    longitudinal    and    transverse,    of    alcoholic 
laterial  are  made,  and  one  of  each  kind  is  stained  with  iodine- 
green.     The  latex  stains  strongly,  and  so  permits  the  ready  iden- 
tification of  the  tissue. 

Focusing  first  with  the  low  power  on  one  of  the  circles  of 
tilk-vessels  in  the  transverse  section,  it  will  be  found  that  the 
vessels  occur  in  clusters  of  various  sizes,  and  that  these  clusters 
are  so  arranged  as  to  form  a  series  of  circles  one  within  the  other. 
These  circles,  each  appearing  to  the  naked  eye  continuous,  give  to 
the  bark  of  this  root  its  concentrically  stratified  appearance.  The 


390  LABORATORY    EXERCISES    IN    BOTANY. 

circles  occur  both  in  the  middle  and  in  the  inner  bark,  but  not  in 
the  wood. 

Under  a  high  power  the  milk-ducts  appear  to  be  of  consid- 
erably smaller  diameter  than  the  neighboring  parenchyma-cells. 
Most  of  them  appear  circular  or  oblong  in  outline  because  the 
knife  has  cut  the  cylindrical  branches  of  the  network  nearly  trans- 
versely, but  others  appear  considerably  elongated,  because  through 
these  the  knife  has  passed  obliquely  or  even  in  the  direction  of 
their  length.  These  are  the  branches  that  cross  over  obliquely  or 
horizontally  and  connect  the  ducts  into  a  network. 

If  now  one  of  the  longitudinal  sections  be  examined,  a  much 
better  idea  of  this  network  of  vessels  will  be  obtained.  The 
parenchyma-cells  in  this  view  are  considerably  elongated,  and  if 
the  section  run  through  one  of  the  clusters  of  milk-ducts  it  will 
be  seen  that  the  tangled  network  of  vessels  has  its  irregular 
meshes  mostly  much  elongated  in  a  direction  lengthwise  of  the 
stem. 

If  the  appropriate  tests  be  applied,  it  will  be  found  that  the 
walls  of  the  milk-vessels  are  of  cellulose,  that  the  latex,  like  the 
rest  of  the  root,  is  destitute  of  starch,  and  that  it  contains  resin- 
ous matters  in  considerable  abundance. 

To  sum  up  the  observations  made,  the  chief  difference  between 
simple  and  complex  laticiferous  tissue  is  that  the  latter  exists  as  a 
complicated  network,  while  the  former  consists  mostly  of  inde- 
pendent tubes.  This  difference  corresponds  to  a  difference  of 
origin.  A  simple  milk-tube  begins  as  an  ordinary  meristem-cell, 
and  grows  as  the  plant  grows,  forming  a  long,  unbranching,  or 
sparingly  branching  tube ;  it  is  at  maturity  still  a  single  cell. 
Complex  laticiferous  tissue,  on  the  other  hand,  is  produced  by  the 
coalescence  of  a  large  number  of  cells  to  form  a  network  of 
anastomosing  tubes.  There  appears  to  be  a  close  relationship 
between  isolated  secretion-cells  and  this  form  of  milk-tissue.  In 
the  Poppy  family,  for  example,  one  finds  in  some  species  only  the 
isolated  secretion-cells;  in  some  others,  as  in  the  Bloodroot,  both 
isolated  secretion-cells  and  those  that  are  arranged  in  chains 
approximating  a  milk-duct  in  appearance  and  structure;  and  in 
the  Poppy  and  Celandine  the  fully-developed  network  of  milk- 
ducts. 

The  fluid  of  milk-tissues  appears  to  be  partly  nutritive,  since 


STUDY    OF    LATICIFEROUS    TISSUE. 


391 


it  contains  albumins  and  carbohydrates ;  but  it  is  partly,  perhaps 
chiefly,  waste  or  excretory,  for  the  resinous  and  some  of  the  min- 
eral matters  can  have  no  nutritive  value  to  the  plant.  The  ex- 
cretory matters,  however,  may  still  serve  the  purpose  of  protection. 
The  latex  is  not  always  of  the  same  color,  but  differs  consider- 
ably in  different  plants :  it  is  often  white  or  yellow,  sometimes 
orange  or  even  deep  orange-red,  as  in  Bloodroot,  but  it  is  some- 
times nearly  colorless,  as  in  the  Oleander. 


STUDY   OF   LATICIFEROUS   TISSUE. 


393 


PLATE  LVII.,  FIG.  1.— Transverse  Section  of  outer  part  of  young  Stem  of  Asclepias 
cornuti :  a,  epidermal  cell ;  b,  cell  of  imperfectly-formed  collenchyma ;  c,  c',  c",  latex- 
tubes  :  d,  an  intercellular  space  in  parenchyma ;  e,  nucleus  of  parenchyma-cell.  (Mag- 
nification, 210  diameters.) 

FIG.  2.— Longitudinal  Section  of  the  same  Stem  through  the  Mesophlceum  :  a,  a  milk- 
tube  which  sends  an  anastomosing  branch  to  an  adjacent  tube;  o,  another  tube  trom 
which  much  of  the  latex  has  escaped ;  c,  one  of  the  parenchyma-cells  among  which  the 
milk-tubes  are  dispersed.  (Magnification,  210  diameters.) 


STUDY   OF    LATICIFEROUS    TISSUE. 


395 


PLATE  LVIIL— A  small  portion  of  the  Cortical  Parenchyma  of  the  Dandelion  root  in 
longitudinal  section,  showing  complex  milk-tissue:  o,  one  of4he  branches  of  the  net- 
work of  milk-vessels ;  6,  one  of  the  parenchyma-cells.  (Magnification  about  170  diameters.) 


EXERCISE    XV. 

STUDY  OF  STAKCHES. 

MOST  of  the  cereals,  such  as  wheat,  rye,  oats,  barley,  and 
maize,  and  many  root-  and  rhizome-drugs,  such  as  sarsaparilla, 
calumba,  belladonna,  bryony,  colchicum,  and  aconite,  afford 
starches  interesting  to  study,  and  many  of  these  starches  show 
very  marked  characteristics. 

I. — For  the  first  part  of  this  study  attention  will  be  given  to 
the  Potato  tuber,  which,  as  has  already  been  learned,  is  rich  in 
starchy  contents. 

Selecting  a  potato  that  is  ripe  or  nearly  so,  a  number  of  sec- 
tions are  made  perpendicular  to  the  corky  exterior,  and  a  few 
others  parallel  to  it.  Let  one  of  the  former  be  mounted  in  a 
drop  of  water,  and  be  examined  first  with  the  low  and  then  with 
a  higher  power. 

At  the  exterior  is  found  a  layer  of  cork  composed  of  from 
fifteen  to  twenty  tiers  of  tabular  cells.  The  outside  layers  of 
this  cork  are  composed  of  shrivelled,  opaque  cells  which  are  more 
or  less  disrupted  and  peeling  off  at  the  surface.  There  is  no 
proper  collenchyma,  but  immediately  interior  to  the  phellogen- 
layer  are  parenchyma-cells  smaller  in  size  and  more  compactly 
arranged  than  those  farther  interior.  They  are  also  richer  in 
proteids  and  much  less  rich  in  starch.  Few  of  the  cells  are  quite 
destitute  of  the  latter,  but  the  granules  are  small.  A  rather 
large  nucleus  and  granular  protoplasm  are  plainly  discernible,  as 
well  as  cubical  crystals  and  rounded  proteid  bodies  of  consider- 
able size. 

In  the  parenchyma  farther  interior  the  cubical  crystals  are 
wanting,  and  the  nucleus,  though  present  in  most  of  the  cells,  is 
often  difficult  to  identify  by  reason  of  the  abundance  of  starch- 
grains  surrounding  it. 

Let  now  a  drop  of  potassium-iodide  iodine  be  placed  at  the 
edge  of  the  cover-glass  and  be  allowed  to  run  under  by  capil- 

397 


398  LABORATORY    EXERCISES    IN    BOTANY. 

lary  attraction.  Watching  the  effects  through  the  microscope,  it 
is  seen  that  as  the  reagent  comes  into  contact  with  the  starch- 
grains  they  become  blue ;  the  color  rapidly  deepens  until  the 
grains  can  no  longer  transmit  light,  and  they  therefore  appear 
black.  The  nucleus,  protoplasm,  and  crystals  stain  brown.  The 
fact  that  the  latter  behave  with  the  reagent  in  a  manner  similar  to 
protoplasm  leads  to  the  inference  that  they  are  not  inorganic  in 
their  nature,  as  might  at  first  be  supposed,  but  are  of  a  proteid 
character,  as  will  be  proved  later  on. 

It  will  be  observed  that  the  small  starch-grains  in  the  exterior 
parenchyma-cells  are  not  usually  isolated,  but  occur  in  groups 
about  granular  masses  of  protoplasm,  and  are  often  clustered  about 
the  nucleus.  The  starch-formers  or  amyloplasts — proteid  particles 
whose  function  it  is  to  build  up  the  starch-grain — occur,  in  fact, 
in  clusters,  and  if  they  could  be  rendered  visible  one  would  be 
found  attached  to  each  young  starch-grain ;  but  in  order  to  render 
them  visible  a  special  method  of  staining  must  be  adopted.  This 
will  be  done  presently ;  but  let  the  structure  of  the  starch-grain 
itself  first  be  studied. 

For  this  purpose  let  scrapings  with  a  knife-blade  from  the 
freshly-cut  surface  of  a  potato  be  made,  and  let  a  small  quantity 
of  these  scrapings  be  placed  on  a  slide  in  a  drop  of  water, 
covered,  and  examined.  By  focusing  on  some  of  the  larger 
grains  it  will  be  seen  that  they  are  mostly  ovate  in  outline,  and 
toward  the  smaller  end  is  noticeable  a  rounded  spot  occasionally 
fissured  by  a  straight  or  angular  fissure,  but  more  commonly 
without  one.  This  fissured  or  unfissured  spot  is  the  hihun  or 
nucleus,  which  marks  the  point  where  the  growth  of  the  grain 
began.  About  the  hi  him  may  be  discerned  a  series  of  curves,  at 
first  concentric,  but  farther  away  becoming  more  and  more  eccen- 
tric. They  are  stratification-lines,  and  their  arrangement  leads  to 
the  conjecture  that  the  growth  was  at  first  nearly  equal,  afterward 
much  greater  on  one  side.  This  conjecture  is  confirmed  by  a  com- 
parison of  young  grains  with  old  or  mature  ones:  in  the  former 
the  hilum  is  nearly  central,  and  if  any  stratification-lines  an-  dis- 
cernible at  all,  they  are  concentric  or  nearly  so;  in  the  mature 
grain  the  hilum  is  much  to  one  side  of  the  centre  and  many  of 
the  curves  are  eccentric. 

If  the  point  of  a  needle  be  gently  laid  on  the  surface  of  the 


STUDY    OF   STARCHES. 

cover  while  the  handle  is  held  in  the  hand,  and  at  the  same  time 
the  starch -grains  be  viewed  through  the  microscope,  the  agitation 
due  to  the  trembling  of  the  hand  will  cause  some  of  the  grains  to 
turn  over  or  turn  up  on  edge,  and  it  may  then  be  seen  that  they 
are  thickest  at  the  hilum  end,  becoming  much  thinner  at  the 
opposite  or  broad  end. 

Attaching  now  the  polariscope  to  the  microscope,  and  viewing 
the  grains  between  the  crossed  Nicol  prisms  with  a  moderate  mag- 
nifying power,  it  will  be  found  that  the  grains  polarize  beautifully, 
and  a  dark,  very  unequal-armed  cross  is  seen  in  each  grain,  the 
arms  of  the  cross  intersecting  at  the  nucleus.  This  effect  is  not 
due  to  crystalline  structure,  for  there  is  no  evidence  of  such  a 
structure  in  starch-grains :  it  is  caused  by  tension  or  strain  among 
the  layers  composing  the  grains. 

Let  an  effort  now  be  made  to  determine  the  cause  of  the  strat- 
ified appearance  of  the  grain.  Placing  a  drop  of  5  per  cent, 
aqueous  solution  of  potassium  hydrate  at  the  edge  of  the  cover- 
glass  and  letting  it  slowly  run  under,  it  will  be  observed  that  as 
soon  as  the  alkali  comes  into  contact  with  the  grain  the  latter  be- 
gins to  swell,  and  for  an  instant  the  stratification-lines  become 
more  distinct ;  but  as  the  swelling  continues  they  grow  indistinct 
and  disappear,  and  finally  the  grain  itself  dissolves. 

These  effects  may  best  be  accounted  for  by  supposing  that  the 
different  layers  contain  normally  different  proportions  of  water, 
and  that  the  more  watery  layers  at  first  absorb  water  under  the 
influence  of  the  alkali  more  rapidly  than  do  the  less  watery  layers, 
and  in  this  way  the  lines  are  brought  out  more  distinctly ;  but 
soon  the  other  layers  begin  to  take  up  water  also,  and  the  lines 
therefore,  as  the  distribution  of  water  becomes  equalized,  dis- 
appear. 

Let  now  a  test  be  applied  to  ascertain  whether  this  theory  is 
correct.  If  it  is  correct,  the  grains  should,  on  thorough  drying, 
lose  their  stratified  appearance.  A  quantity  of  starch  is  there- 
fore heated  on  some  slides  for  a  time  at  a  temperature  sufficiently 
high  to  evaporate  the  water,  but  too  low  to  destroy  the  structure 
of  the  grain — say,  a  temperature  of  60°  Centigrade.  If  then  the 
grains  be  mounted  in  some  liquid  that  contains  no  water  and  yet 
is  not  too  refractive  to  permit  of  seeing  the  grains  distinctly — as 
a  solution  of  dammar  in  equal  parts  of  oil  of  turpentine  and 


400  LABORATORY    EXERCISES    IN    BOTANY. 

benzol,  for  example — the  Hues  will  be  found  to  have  disappeared. 
But  the  proof  may  be  strengthened  by  means  of  the  following 
experiment :  Taking  some  of  the  thoroughly  dried  grains,  they 
are  treated  on  the  slide  with  a  5  per  cent,  solution  of  silver 
nitrate  in  distilled  water,  the  liquid  being  allowed  to  remain  in 
contact  with  the  starch  for  an  hour  or  more;  draining  away  the 
reagent  and  drying  the  grains,  they  are  treated  for  an  hour  or 
more  with  5  per  cent,  solution  of  common  salt,  and  then,  after 
rinsing  in  clean  water,  they  are  exposed  for  an  hour  or  more  to 
the  bright  sunshine.  If  it  be  a  fact  that  some  of  the  layers  are 
capable  of  taking  up  more  water  than  others,  the  silver  chloride 
will  have  been  precipitated  more  abundantly  in  these  layers,  and 
when  the  chloride  has  been  reduced  by  the  action  of  sunlight  the 
stratification  of  the  grains  should  appear  very  distinct.  The  ex- 
periment, if  properly  tried,  fully  justifies  expectations  and  bears 
out  the  theory. 

Studying  the  structure  of  the  grains  still  further,  it  is  found 
that  some  are  double,  containing  two  nuclei,  each  with  the  con- 
centric and  eccentric  markings  about  it,  and  a  dividing-line  dis- 
tinctly recognizable  between  the  two  portions  of  the  grain  ;  some- 
times even  triple  grains  are  found.  In  other  instances  the  grains 
are  not  properly  double  or  triple,  but  are  binucleated  or  trinucle- 
ated.  Each  nucleus  has  a  few  concentric  curves  about  it,  but 
exterior  to  these  are  curves  which  belong  to  the  entire  grain  and 
enclose  all  the  nuclei.  In  many  starches — as,  for  example,  tlm-e 
of  the  sarsaparillas  and  of  the  oat — compound  and  multiniicleated 
grains  are  the  rule,  and  not  the  exception.  There  are  great  dif- 
ferences also  among  the  starches  of  diifereut  plants,  not  only  in 
the  size  and  shape  of  the  grains,  but  in  the  position  of  the  hiluin 
(whether  central  or  eccentric),  in  the  number  and  distinctness  <>f 
the  stratification-lines,  in  the  degree  to  which  the  hilum  is  fissured, 
and  in  the  character  of  the  fissures. 

Let  now  an  endeavor  be  made  to  render  visible  the  amyloplaM-. 
To  do  this  let  some  of  each  of  the  kinds  of  sections  prepared  be 
placed  in  a  saturated  aqueous  solution  of  bichloride  of  mercury, 
and  be  allowed  to  remain  there  for  twelve  hours  to  fix  the  pro- 
teids.  Afterward  they  should  be  washed  thoroughly  in  dilute 
alcohol  to  remove  the  bichloride.  The  sections  are  then  placed 
in  a  dilute  solution  of  acid  fuchsin  for  half  an  hour,  rinsed  well 


STUDY    OF    STARCHES.  401 

in  water  to  remove  the  color  from  the  cell-walls,  anhydrated, 
treated  very  briefly  with  oil  of  cloves,  and  mounted  in  xylol 
balsam. 

Placing  one  of  the  preparations  under  the  microscope  and 
focusing  upon  some  of  the  parenchyma-cells  but  little  interior  to 
the  cork,  it  will  be  found  that  the  cubical  crystals  already  referred 
to  have  been  stained  a  deep-red  color,  that  granular  particles  in 
the  nucleus  have  also  stained  the  same  color,  that  other  rounded 
or  but  slightly  angular  bodies  have  stained  in  the  same  way,  and 
that  attached  to  the  ends  or  sides  of  some  of  the  smaller  or 
medium-sized  starch-grains  are  similarly  stained  bodies.  The 
latter  are  the  amyloplasts.  These  bodies  are  in  their  nature  sim- 
ilar to  chlorophyll  bodies,  but  without  the  chlorophyll,  and  there 
are  the  best  of  reasons  for  believing  that  most  starch-grains  are 
formed  by  the  agency  of  either  the  one  or  the  other.  In  a  few 
instances,  however,  they  are  believed  to  be  formed  by  the  agency 
of  ordinary  protoplasm. 

It  is  more  than  ever  evident  that  the  cubical  crystals  are  pro- 
teid  bodies,  for  they  have  stained  like  them.  They  are,  in  fact, 
good  examples  of  protein  crystals  or  crystalloids.  In  the  potato 
they  are  mostly  cubical,  but  some  may  be  found  with  the  corners 
and  angles  rounded  off  so  that  they  are  nearly  spherical. 

If  a  fresh  section  be  taken,  and,  having  focused  the  micro- 
scope on  one  of  the  crystalloids,  a  drop  of  potassium-hydrate 
solution  be  allowed  to  run  under  the  cover-glass,  the  crystalloid 
will  be  observed  to  swell,  to  lose  its  sharp  angles,  and  finally  to 
disappear.  This  behavior  is  that  of  a  proteid,  but  not  that  of 
an  inorganic  crystal. 

II. — Let  attention  now  be  directed  to  a  different  starch,  that 
of  Colchicum  autumnale.  It  will  be  sufficient  to  scrape  upon  a 
slide  a  little  of  the  tissue  from  the  cut  surface  of  one  of  the 
dried  sections  of  the  corm  commonly  sold  at  apothecary  shops, 
and  to  mount  the  scrapings  in  a  drop  of  water.  Starch-grains 
will  be  seen  in  great  abundance,  but  ones  very  different  from 
those  observed  in  the  potato.  They  are  not  only  much  smaller 
and  different  in  shape,  but  the  hilum  is  central  or  nearly  so,  and 
very  strongly  and  distinctly  fissured  even  in  the  more  minute 
grains.  The  fissures  are  usually  stellate,  but  sometimes  consist 
of  a  single  straight  or  curved  slit.  Moreover,  the  majority  of 

26 


402  LABORATORY    EXERCISES   IN   BOTANY. 

the  grains  are  seen  either  in  clusters  of  two,  three,  or  more,  or 
else  the  squared  ends  or  sides  show  that  the  grains  have  been  a 
part  of  such  clusters.  There  is,  however,  a  goodly  sprinkling  of 
grains  that  are  strictly  simple,  and  these  are  all  spherical  or 
nearly  so. 

Stratification-curves  are  in  this  species  difficult  to  detect  with- 
out resort  to  the  silver-nitrate  process,  by  which,  however,  a  few 
strata  may  be  seen,  though  they  are  not  nearly  so  numerous  as  in 
the  starch  of  the  potato. 


STUDY   OF   STARCHES. 


403 


a 


PLATE  LIX— A  small  portion  of  a  Cross-section  of  the  Potato  Tuber,  showing  the  cork 
and  a  little  of  the  sublying  parenchyma:  a,  old  cork;  b,  younger  but  mature  cork;  c, 
youngest  cork-cells ;  d,  phellogen  layer ;  e,  nucleus  of  one  of  the  parenchyma-cells, 
which  also  contains  a  cubical  crystalloid  ;  /,  crystalloid  ;  g,  small  starch-grains ;  h,  inter- 
cellular space  ;  i,  larger  starch-grain,  showing  hilum  and  stratification-curves.  (Magni- 
fication, 120  diameters.) 


STUDY    OF   STARCHES. 


405 


.TE  LX.,  FIG.  1— Starch  from  Potato  (magnified  305  diameters) :  a,  a  bi-nucleated 
grain ;  6,  a  double  grain ;  c,  a  grain  as  seen  under  the  polariscope. 
FIG.  2.— Starch  from  the  Corm  of  Colchicum  autumnale  (magnified  310  diameters). 


EXERCISE  XVI. 
STUDY  OF  ALEURONE-GRAINS. 

THE  seeds  of  the  following  plants  afford  interesting  material : 
Croton  Tiglium,  i.,  Ricinus  communis,  L.,  Bertholletia  excelsa, 
Humboldt  and  Bonpland,  Pisum  sativum,  L.,  Delphinium  Staph- 
isagria,  L.,  Lupinus  varius,  L.,  and  Triticuni  vulgare,  Villars. 

Most  plants  lay  up  some  portion  of  their  reserve  food  mate- 
rial in  the  form  of  albuminous  matters  of  various  kinds,  as  well 
as  in  the  form  of  starch,  oil,  inulin,  and  sugar.  One  of  the  most 
important  of  the  albuminous  reserve  food  materials  is  aleuroue, 
found  chiefly  in  seeds,  and  most  abundantly  in  oily  ones.  It 
usually  occurs  in  the  form  of  rounded  granules  which  are  often 
quite  small,  but  which  sometimes  attain  a  considerable  size,  as  in 
the  Croton  and  Castor  Beans  and  in  the  Brazil-nut.  In  many  cases 
the  granules  appear  to  be  homogeneous  in  structure  or  nearly  so, 
but  in  other  cases  they  contain  various  substances  differing  more 
or  less  in  constitution  from  the  main  body  of  the  grain.  These 
substances  may  be  oily  matters,  mineral  crystals,  and  crystalloids. 

For  this  study  is  selected  the  endosperm  of  the  Castor  Bean. 
On  removing  the  seed-coats  the  endosperm  will  be  found  in  good 
condition  for  sectioning  without  further  preparation. 

A  number  of  thin  sections  should  be  cut  and  be  set  aside,  but 
not  in  liquid,  until  required  for  use  as  directed. 

A  section  is  first  mounted  in  a  drop  of  strong  glycerin,  and 
after  finding  the  thinnest  part  of  the  section  with  the  low  power 
it  is  focused  upon  with  the  higher  one.  The  aleurone-grains  are 
seen  as  rather  large,  nearly  spherical  or  ellipsoidal  bodies  occupy- 
ing the  larger  portion  of  the  interior  of  the  cells.  In  appearance 
they  are  not  unlike  starch -grains,  but  appropriate  tests  easily  prove 
their  proteid  nature,  and  prove  also  that  this  seed  does  not  con- 
tain starch.  The  aleurone  is  intermixed  with  finely  granular  and 
rather  opaque  matters  consisting  of  a  mixture  of  fats  and  amor- 
phous proteids. 

407 


408  LABORATORY    EXERCISES    IN    BOTANY. 

At  first  the  aleu rone-grains  appear  homogeneous,  but  presently 
the  clearing  action  of  the  glycerin  comes  into  play,  and  through 
the  now  more  transparent  exterior  portion  of  the  grain  is  seen  a 
denser,  many  sided  body,  the  crystalloid,  which  is  often  so  large 
that  the  rest  of  the  grain  forms  scarcely  more  than  a  pellicle  about 
it.  At  other  times,  however,  the  crystalloid  is  relatively  much 
smaller,  or  the  grain  may  even  contain  two  or  more  crystalloids. 
There  are  also  usually  seen  on  the  interior  of  the  grain,  along- 
side of  the  crystalloid,  one  or  more  small,  globular,  strongly 
refractive  bodies  called  globoids.  They  are  not  organic  in  their 
nature,  being  composed  of  the  double  phosphate  of  calcium  and 
magnesium. 

If  now  the  cover-glass  be  removed,  and,  after  adding  a  drop 
of  the  strong  potassium-iodide  iodine  and  allowing  it  a  few 
minutes  to  penetrate  the  structure,  it  be  replaced  and  the  section 
again  be  examined,  the  grains  will  be  found  to  have  acquired  a 
brown  color,  especially  deep  in  the  crystalloids.  The  reaction  in- 
dicates their  proteid  character.  The  globoids  remain  unstained. 

If  there  be  applied  to  a  section  a  drop  of  1  or  2  per  cent. 
solution  of  potassium  hydrate,  the  crystalloids  will  swell  rap- 
idly, lose  their  angles,  and  disappear  as  did  those  observed  in  the 
potato. 

If  now  a  fresh  section  be  placed  upon  the  slide,  covered,  and 
a  drop  of  water  be  allowed  to  run  under  the  cover-glass,  the  oil 
will  be  observed  to  run  together  and  to  form  drops,  probably  from 
the  solution  of  the  albuminous  pellicles  which  keep  the  minute 
droplets  apart;  the  oil  flows  out  of  the  ruptured  tissues,  and 
may  soon  be  observed  in  drops  at  the  borders  of  the  section  as 
well  as  in  some  of  the  cells.  As  the  water  comes  into  contact 
with  the  aleurone-grains  their  ground-substance  swells  and  rather 
rapidly  disappears  from  view,  leaving  the'  crystalloids  for  a  feu- 
moments  standing  out  sharp  and  clear;  but  soon  these  too  bruin 
to  swell  and  to  lose  their  angles,  though  it  takes  them  a  long  time 
to  disappear  wholly. 

If,  while  the  crystalloids  are  still  sharply  defined,  there  he 
allowed  to  run  under  the  cover-glass  some  absolute  alcohol,  the 
structure  of  the  grains  may  still  better  be  seen,  the  ground-sub- 
stance beinir  still  visible  but  transparent,  and  the  crystalloids  and 
globoids  being  sharply  defined  on  the  interior.  Still  more  pleas- 


STUDY   OF    ALEURONE-GRAINS.  409 

ing  results,  however,  may  be  obtained  by  one  of  the  following 
processes : 

(1)  Place  a  few  of  the  sections,  cut  as  thin  as  possible,  in  a  5 
per  cent,  alcoholic  solution  of  bichloride  of  mercury  to  fix  them, 
permitting  them  to   remain  in  the  solution   for  several   hours ; 
then  remove  the  sections  from  the  fixing  solution,  and,  having 
washed  them  thoroughly  in  alcohol  to  get  rid  of  the  bichloride, 
place  them  for  fifteen  or  twenty  minutes  in  a  rather  dilute  solu- 
tion of  acid  fuchsin  ;  then  rinse  them  well  in  water  or  dilute  alco- 
hol to  remove  the  bulk  of  the  stain  from  the  cell-walls,  anhy- 
drate  them,  pass  them  rather  rapidly  through  oil  of  cloves,  and 
mount  them  in  xylol  balsam.     In  this  way  the  crystalloids  will 
be  stained  a  deep-red  color,  while  but  slight  traces  of  color  will 
remain  in  the  ground-substance  and  in  the  cell-walls,  so  that  the 
crystalloids  appear  very  sharply  defined. 

(2)  The  second  method  is  quite  as  satisfactory  and  is  much  more 
rapid.     The  sections  are  first  treated  for  about  twenty  minutes  or 
half  an  hour  with  a  dilute  aqueous  solution  of  tannin,  are  rapidly 
rinsed  in  pure  water,  and  are  transferred  to  a  1  or  2  per  cent,  solu- 
tion of  osmic  acid  in  distilled  water.    They  are  allowed  to  remain 
in  this  solution  only  a  few  moments,  when  they  are  thoroughly 
washed   in  pure  water  to  get  rid  of  the  last  traces  of  the  acid. 
This  is  necessary,  because  if  not  done  the  section  will  ultimately 
become  so  opaque  that  the  structure  cannot  be  recognized.     The 
crystalloids  now  appear  stained  a  deep-brown  color,  while  the 
ground-substance  is  only  very  slightly  stained.     If  desired,  the 
sections  may  be  mounted  permanently  in  glycerin  gelatin  or  be 
anhydrated  by  means  of  absolute  alcohol  and  mounted  in  balsam. 

x  Since  the  sections  contain  fixed  oil,  a  few  minutes  may  profit- 
ably be  spent  in  learning  to  apply  the  tests  for  its  recognition. 
Had  what  took  place*  when  one  of  the  sections  w^as  treated  with 
absolute  alcohol  been  observed  closely,  it  would  have  been  seen 
that  the  oil-globules  gradually  disappeared  from  view.  This 
is  because  castor  oil  is  one  of  the  very  few  fixed  oils  which  are 
freely  soluble  in  alcohol. 

NOWT  let  a  fresh  section  be  treated  with  a  few  drops  of  the 
ilcannin  solution,  and  it  will  be  found  after  a  few  minutes  that 
the  oil-globules  that  have  flowed  out  around  the  margins  of  the 
:ion,  as  well  as  those  that  have  formed  in  the  cells,  and  even 


410  LABORATORY    EXERCISES    IN    BOTANY. 

the  fine  granules  in  the  cell,  not  otherwise  optically  distinguish- 
able as  oil-drops,  have  stained  a  deep-red  color.  In  this  behavior 
fats  agree  with  volatile  oils  and  resins,  but  differ  from  all  other 
substances. 

Lastly,  let  another  section  be  mounted  dry,  the  cover-glass  being 
pressed  down  rather  strongly,  so  as  to  force  some  of  the  oil  out  of 
the  cells  to  the  edge  of  the  section.  If  now  a  drop  of  the  cyan  in 
solution  be  allowed  to  run  under  the  cover-glass,  the  refractive 
globules  of  oil  will  soon  be  stained  a  brilliant  blue. 

Fixed  oils,  like  aleurone-grains  and  starch,  serve  the  plant  as 
reserve  food  materials.  They  occur  in  a  very  large  proportion  of 
seeds  and  spores,  and  sometimes  constitute  the  greater  part  of  their 
weight. 

Crystalloids  also  most  often  occur  in  seeds,  but  sometimes  else- 
where in  the  plant.  They  occur  in  the  epidermis  of  the  Ivy,  in 
the  young  shoots  of  the  Canna,  in  the  vegetative  parts  of  many 
marine  algae,  in  the  mycelium  of  a  few  fungi,  and  in  minute  form 
they  have  been  observed  in  the  nuclei  of  the  cells  of  various  plants. 


STUDY    OF    ALEURONE-GKAINS. 


411 


PLATE  LXL— A  few  Cells  from  the  Endosperm  of  Ricinus  commnnis,  showing  aleu- 
rone-grains,  their  contained  crystalloids  and  globoids,  and  the  granular  ground  sub- 
stance of  the  cells,  containing  proteids  and  oil  (magnification,  330  diameters).  Drawing 
made  from  a  section  which  had  been  treated  by  the  tannin-osmic-acid  process,  a,  a,  crys- 
talloids in  aleurone-grains  ;  b,  granular  ground  substance  of  cell ;  c,  a  globoid. 


EXERCISE  XVII. 

STUDY  OF  CHLOKOPLASTS  AND   COLORING   MATTERS. 

CHLOROPLASTS  or  chlorophyll  bodies  occur  in  nearly  all  green 
plants ;  but,  since  in  many  of  the  higher  species  these  bodies  are 
quite  small  and  often  very  much  crowded  in  the  cells,  selections 
for  study  would  better  be  made  from  some  of  the  following  plants : 
any  of  the  larger-leaved  mosses  or  liverworts ;  the  upper  part  of 
the  thallus  of  the  Common  Marchantia  (Marchantia  polymorpha, 
L.) ;  the  prothallia  of  almost  any  species  of  fern ;  the  leaves  of 
some  aquatic  phanerogams,  as  those  of  the  Tape-  or  Eel-grass 
(Vallisneria  spiralis,  L.\  of  the  Water-weed  (Elodea  Canadensis, 
Michx.),  and  of  the  more  transparent-leaved  species  of  Pondweed 
(Potamogetou) ;  many  of  the  fresh-water  alga3,  as  the  members 
of  the  genus  Spirogyra,  where  the  chloroplasts  form  spiral  bauds 
in  the  cells,  and  the  members  of  the  genus  Zygnema,  where  they 
have  a  stellate  form,  will  also  afford  interesting  comparative  stud- 
ies. Suitable  mosses,  Marchantia,  and -fern  prothallia  may  be 
found  growing  on  the  flower-pots  and  damp  walls  of  greenhouses 
at  any  season  of  the  year. 

In  the  great  majority  of  cases  chloroplasts  are  rounded  or 
ellipsoidal  bodies;  they  very  rarely  take  such  shapes  as  those 
of  Spirogyra  or  Zyguema.  They  are  proteids,  perhaps  to  be 
regarded  as  a  part  of  the  living  protoplasm  of  the  cell,  since 
they  have  the  power  of  growth  and  division.  Wherever  they 
occur  they  are  intimately  associated  with  ordinary  protoplasm, 
being  imbedded  in  the  more  granular  portions  of  it  and  being 
carried  about  by  its  movements.  These  movements  are  influenced 
by  the  light  which  falls  upon  the  cells,  so  that  the  positions  occu- 
pied by  the  chloroplasts  in  darkness  or  when  the  light  is  weak  are 
different  from  those  occupied  by  them  when  the  light  is  intense. 

I. — Let  chloroplasts  as  found  in  a  moss  leaf  first  be  studied. 

Placing  the  leaf  of  a  moss,  plucked  fresh  from  the  living 
plant,  on  a  slide,  and  mounting  it  in  a  drop  of  water,  there  will 

413 


414  LABORATORY    EXERCISES    IN    BOTANY. 

be  seen  great  numbers  of  distinctly  outlined  green  bodies  among 
the  otherwise  colorless  cell-contents.  These  green  bodies  are  the 
chloroplasts,  the  bodies  which  communicate  the  color  to  all  the 
green  parts  of  a  plant.  Viewing  them  with  the  high  power,  they 
are  seen  to  be  for  the  most  part  spherical  or  nearly  so ;  but  some 
are  rather  elongated  or  oblong  in  outline,  and  occasionally  one 
may  be  seen  that  is  elongated  and  strongly  contracted  midway 
between  its  two  ends.  The  latter  two  forms  represent  successive 
stages  in  the  process  of  division,  the  form  with  a  constriction  in 
its  middle  being  nearly  ready  to  separate  into  two. 

If  now  a  few  drops  of  alcohol  be  permitted  to  run  under  the 
cover-glass  and  the  effects  be  observed,  it  will  be  seen  that  the 
green  color  gradually  fades  out  of  the  chloroplasts  without  other- 
wise changing  their  form  or  appearance ;  as  this  change  takes  place 
the  cell-sap  acquires  a  clear-green  color.  The  chlorophyll — that 
is,  the  green  coloring  matter — has  dissolved  in  the  alcohol.  The 
chloroplast  and  the  chlorophyll  which  it  contains  are  therefore 
distinct  things. 

An  instructive  experiment  is  to.  crush  a  few  green  leaves — such 
as  those  of  the  Hyacinth,  for  example — to  treat  them  with  strong 
alcohol,  and,  after  the  mixture  has  macerated  for  half  an  hour, 
to  filter  off  the  alcoholic  solution.  Much  of  the  chlorophyll  will 
have  passed  into  solution  in  the  alcohol,  and  the  liquid  will  have1 
acquired  a  color  which  by  transmitted  light  is  a  vivid  green,  but 
by  reflected  light  is  a  deep  red. 

Returning  now  to  the  leaf  of  the  moss,  one  that  has  had  the 
chlorophyll  removed  from  it  by  the  action  of  alcohol  is  mounted 
in  a  drop  of  potassium-iodide  iodine.  The  ordinary  protoplasm 
and  cell-nucleus,  previously  so  transparent  as  to  be  invisible,  are 
now  distinctly  seen  by  reason  of  the  brownish  color  they  have 
acquired,  and  chloroplasts  also  show  their  proteid  nature  by  hav- 
ing acquired  a  deep-brown  color. 

One  of  the  chief  functions  of  chloroplasts  is  to  form  starch  ; 
this  is  accomplished  through  the  agency  of  the  light  acting 
upon  the  contained  chlorophyll.  The  starch  thus  formed  is 
for  the  time  being  laid  up  in  the  form  of  minute  corpuscles  in 
the  interior  of  the  chloroplasts.  Ordinarily,  however,  these 
starch  -corpuscles  are  invisible,  but  they  may  be  brought  to  view 
by  means  of  appropriate  tests.  The  following  process  may  be 


STUDY   OF   CHLOROPLASTS   AND   COLORING   MATTERS.      415 

adopted  to  demonstrate  their  presence :  Placing  a  drop  of  potas- 
sium-hydrate solution  at  the  edge  of  the  cover-glass  of  the  iodine- 
stained  specimen  just  examined,  and  letting  it  run  under,  the 
section  is  watched  through  the  microscope  to  observe  what  takes 
place.  As  the  alkaline  liquid  comes  into  contact  with  the  chlor- 
oplasts  they  swell  and  become  transparent,  momentarily  revealing 
the  blue-stained  starch-grains ;  but  these  very  soon  lose  their 
color,  swell,  and  presently  disappe'ar  from  view. 

A  better  method,  therefore,  is  the  following :  Apply  to  a  leaf 
that  has  been  bleached  by  alcohol  a  drop  or  two  of  chloral-hydrate 
iodine.  This  would  better  be  done  by  mounting  the  leaf  in  a 
drop  of  water,  and  then,  after  focusing  the  microscope,  placing  a 
drop  of  the  reagent  at  the  edge  of  the  cover,  because  it  is  import- 
ant to  observe  the  beginnings  of  the  reaction.  When  the  reagent 
comes  into  contact  with  the  chloroplasts  they  swell  rapidly  and 
become  transparent,  revealing  the  starch-granules,  which  swell 
much  more  slowly  and  are  stained  blue,  by  the  iodine.  Presently 
the  chloroplast  completely  disappears  from  view,  leaving  the 
starch-granules  standing  out  sharp  and  clear.  They  will  be  seen 
to  be  mostly  oblong,  rod-like,  or  crescent-shaped  bodies,  some  of 
them  being  exceedingly  minute.  There  are  usually  several  gran- 
ules in  each  chloroplast. 

In  a  study  of  this  kind  it  is  important  that  the  leaves  be  taken 
from  vigorously  growing  plants  that  have  been  exposed  to  sun- 
light some  hours  immediately  before  fixation  and  bleaching  in 
alcohol,  otherwise  the  chloroplasts  may  contain  little  or  no  starch, 
for  at  night  or  in  darkness  the  starch  that  accumulates  in  the 
chloroplasts  during  the  daylight  is  dissolved  and  transferred  to 
other  parts  of  the  plant. 

II. — The  colors  of  flowers  are  due  to  various  causes :  some- 
times to  proteid  corpuscles  similar  in  their  nature  to  chloroplasts, 
but  containing  some  other  coloring  matter  different  from  chloro- 
phyll ;  sometimes  to  a  coloring  principle  in  solution  in  the  cell- 
sap  ;  and  sometimes  to  crystalline  coloring  matters  in  the  cells. 
Most  of  the  shades  of  yellow  and  orange,  and  in  rare  instances 
some  of  the  blues,  are  due  to  color-corpuscles,  but  these  are  sel- 
dom so  definite  in  form  or  so  well  defined  as  are  chlorophyll- 
corpuscles.  Not  infrequently,  however,  these  color-corpuscles  are 
produced  by  changes  in  the  chloroplasts,  and  the  colors  they  con- 


41 G  LABORATORY    EXERCISES   IN    BOTANY. 

tain  are  the  product,  in  some  instances  at  least,  of  chemical  changes 
in  the  chlorophyll.  This  is  the  fact,  probably,  with  many  of  the 
colors  of  autumn  leaves. 

Anthoxanthiu  is  the  coloring  principle  which  is  perhaps  the 
commonest  in  the  color-corpuscles  of  yellow  flowers. 

Most  of  the  shades  of  violet,  blue,  and  red,  as  well  as  now  and 
then  a  yellow,  are  due  to  coloring  matters  in  solution  and  diffused 
through  the  cell-sap.  Erythrophyll  is  the  commonest  of  the  red 
coloring  matters  belonging  to  this  category,  and  anthocyaniu  is 
the  commonest  of  the  blues. 

Flowers  of  any  of  the  following  plants  may  be  studied  with 
profit:  the  Nasturtium  (Tropeolum  majus,  L.),  the  Allamanda 
(Allamanda  Schottii,  Pohl),  the  Spiderwort  (Tradescantia  Yirgin- 
ica,  L\  the  Toad-flax  (Linaria  vulgaris,  Mill.),  the  red-flowered 
form  of  the  Shrubby  Mallow  (Hibiscus  Syriacus,  L.),  and  the 
Eed  Rose  (Eosa  Gallica,  L.). 

From  this  list  is  selected  for  special  study  the  flower  of  Linaria 
vulgaris,  a  plant  now  common  throughout  the  Eastern  United 
States,  and  known  under  the  popular  names  of  "  Snapdragon," 
"  Butter-and-Eggs,"  and  "  Toad-flax."  The  corolla  is  gamopet- 
alous,  bilabiate,  and  strongly  calcarate.  The  prevailing  color  is 
lemon-yellow,  but  the  palate  is  orange-colored.  The  latter  is  also 
provided  with  numerous  striated  hairs.  The  most  favorable  por- 
tions for  study  are  not  the  most  deeply  colored  ones,  for  the  hairs 
and  the  conical  elevations  on  the  epidermal  cells  interfere  witli 
the  view  of  the  cell-contents. 

A  specimen  is  therefore  prepared  as  follows :  Seizing  one  of 
the  lips  with  each  hand,  the  lower  lip  is  sharply  bent  back  and 
the  flower  is  torn  down  through  the  spur  to  the  apex  of  the  latter. 
The  epidermis  will  in  most  cases  strip  off  from  the  spur  by  this 
method,  and  after  cutting  away  the  other  portions  with  scissors  it 
may  be  mounted  in  a  drop  of  water  and  be  examined. 

The  cells  will  be  found  to  contain  a  light-yellow  coloring  mat- 
ter dissolved  in  the  cell-sap.  Besides  this  there  may  with  sonic 
difficulty  be  made  out  the  cell-nucleus  and  the  nearly  transparent 
protoplasm.  There  are  also  present  some  small,  rounded,  dense, 
and  colorless  particles  which  the  iodine  test  would  prove  to  be 
starch-grains, 

But  the  diffused  yellow  coloring   matter  is  not  the  only  <>ne 


STUDY    OF    CHLOROPLASTS    AND   COLORING    MATTERS.       417 

present  in  this  case.  In  some  parts  of  the  epidermis,  though  not 
in  all,  will  be  found  numerous  small  crystals  of  a  distinctly  yel- 
low color  and  of  very  various  shapes :  some  are  prismatic  and 
square-ended,  others  are  prismatic  and  have  the  ends  terminated 
by  pyramids,  others  are  in  the  form  of  two  pyramids  placed  base 
to  base ;  many  are  elongated  into  acicular  forms,  some  are  tabu- 
lar, and  still  others  form  globular  or  stellate  masses,  each  mass 
showing  a  distinctly  radial  structure.  Viewed  by  polarized  light, 
the  crystals  give  splendid  polarization  effects,  but  with  reagents 
their  behavior  is  quite  different  from  that  of  the  ordinary  min- 
eral crystals  found  in  plants.  If  treated  with  potassium -hydrate 
solution,  they  quickly  dissolve  and  disappear,  at  the  same  time 
communicating  to  the  tissue  a  red  or  orange-red  color.  The  effect 
of  the  solution  is  most  striking  if  the  crystals  be  viewed  by 
polarized  light  while  the  potassium  hydrate  is  permitted  to  run 
under  the  cover-glass. 

The  crystals  are  also  dissolved,  only  a  little  more  slowly,  by 
means  of  the  chloral-hydrate  iodine  solution.  This  reagent  also 
establishes  the  fact  that  fine  starch-grains  exist  in  the  cells,  and 
most  abundantly  in  those  which  contain  fewest  of  the  crystals. 

The  crystals  are  insoluble  in  acetic  acid,  but  dissolve  slowly  in 
hydrochloric  acid,  more  rapidly  in  sulphuric  acid,  and  in  both  in- 
stances with  the  production  of  a  red  color.  In  alcohol  they  are 
insoluble. 

In  the  bright-yellow  corolla  of  Allamanda  the  color  resides  in 
small,  mostly  rounded  corpuscles  which  do  not  polarize  light, 
which  are  insoluble  in  potassium-hydrate  solution  and  in  alcohol^ 
which  are  quickly  stained  a  deep-red  color  by  alcanniu  solution, 
and  which  are  also  stained  a  deep  blue,  though  more  slowly,  by 
cyan  in  solution. 

If  the  epidermis  be  stripped  off  from  the  lower,  deep-red  por- 
tion of  the  petal  of  Hibiscus,  and  be  mounted  in  water,  the  cells 
will  appear  to  be  filled  with  a  bright-red  sap  in  which  the  cell- 
nucleus  is  visible  as  a  lighter  spot.  No  granular  coloring  matter 
exists  in  these  cells. 

27 


STUDY   OF   CHLOROPLASTS   AND   COLORING   MATTERS.      419 


1 


PLATE  LXIL,  FIG.  1.— A  few  Cells  from  the  Leaf  of  a  Moss,  showing  numerous  chloro- 
plasts  and  finely  granular  protoplasm  in  the  cells  (magnified  535  diameters). 

FIG.  2.— A  few  Cells  from  the  same  Leaf  after  treatment  with  chloral-hydrate  iodine, 
which  has  destroyed  the  chloroplasts,  leaving  the  small  starch-grains  which  they  con- 
tained undissolved,  but  somewhat  swollen  (magnified  535  diameters). 


STUDY   OF   CHLOROPLASTS   AND    COLORING   MATTERS.     421 


PLATE  LXIII.,  FIG.  1.— Three  of  the  Chloroplasts  from  the  Leaf  of  a  Moss,  somewhat 
swollen  and  rendered  transparent  by  the  chloral,  but  not  yet  dissolved,  showing  the 
starch-granules  in  their  interior  (magnification,  800  diameters). 

FIG.  2.— Portion  of  Epidermis  of  the  Corolla-spur  of  Linaria  vulgaris,  showing  color- 
crystals  (magnification,  535  diameters). 


EXERCISE  XVIII. 
STUDY  OF  INULIN  AND  SUGAR 

I. — THE  roots  of  any  of  the  following  plants,  if  collected  in 
autumn,  contain  inulin  in  abundance,  and  afford  convenient  objects 
for  the  study  of  this  carbohydrate :  the  Dandelion  (Taraxacum 
officinale,  Weber),  the  Chicory  (Cichorium  Intybus,  _L.),  the  Sal- 
sify (Tragopogou  porrifolius,  Z/.),  the  Burdock  (Arctium  Lappa, 
Z.),  the  Pellitory  (Anacyclus  Pyrethrum,  DC.\  the  Sow- 
thistle  (Souchus  oleraceus,  Z.),  and  the  Elecampane  (Inula  Hele- 
nium,  Z.). 

Inulin,  though  resembling  starch  in  its  chemical  nature,  and 
serving  the  same  purpose  in  the  plant,  does  not  naturally  occur  in 
the  form  of  solid  particles,  but  in  solution  in  the  cell-sap.  It 
may,  however,  be  obtained  in  the  crystalline  form  by  taking 
advantage  of  its  insolubility  in  strong  alcohol. 

The  roots  of  Chicory  are  selected  for  this  study.  They  should, 
immediately  after  removal  from  the  soil  and  washing,  be  cut  into 
pieces  a  centimetre  or  a  centimetre  and  a  half  long,  be  placed  in 
strong  alcohol,  and  be  allowed  to  remain  there  for  some  time — 
at  least  several  days.  The  inulin  gradually  crystallizes  out,  and 
may  then  be  seen  in  the  cells  and  intercellular  spaces  of  the 
plant. 

Sections,  either  transverse  or  longitudinal,  of  the  root  may  be 
made  and  be  mounted  either  in  strong  alcohol  or  in  strong  glycerin 
for  study.  The  crystals  dissolve  too  rapidly  if  mounted  in  aque- 
ous fluids.  They  may  be  seen  under  the  low  power  as  spherical, 
spheroidal,  or  nodular  masses  in  the  cells,  and  particularly  in  the 
radial,  fissure-like,  intercellular  spaces  in  the  bark.  They  are 
transparent  and  refractive,  and  they  show  a  central  dark  spot  or 
radial  fissure  and  several  concentric  circles  as  well  as  numerous 
fine  radial  lines.  The  masses  are  not  always  spherical :  sometimes 
they  are  hemispherical  and  formed  against  one  side  of  the  cell- 

423 


424  LABORATORY    EXERCISES   IN    BOTANY. 

wall,  and  sometimes  there  may  even  be  found  a  sphere-crystal 
which  is  bisected  by  the  cell-wall,  one-half  of  the  crystal  lying 
on  one  side  of  the  wall,  the  other  half  on  the  other  side.  Some- 
times several  of  the  crystalline  spheres  starting  from  neighbor- 
ing centres  will  be  seen  to  have  coalesced  to  form  a  nodular 
mass,  each  part,  however,  preserving  its  concentric  and  radial 
structure. 

The  markings  and  the  structure  of  these  sphere-crystals  are 
better  seen  if  a  section  be  treated  for  a  few  minutes  with  strong 
alcoholic  solution  of  iodine,  which  penetrates  between  the  fine 
crystals  composing  the  mass,  staining  it  yellowish.  The  effects 
of  the  stain  will  show  more  distinctly  if  the  section,  after  re- 
moval from  the  iodine,  be  dipped  for  a  moment  in  alcohol  to 
wash  away  the  excess  of  iodine ;  but  this  immersion  must  not  be 
of  too  long  duration,  or  the  whole  structure  will  be  decolorized. 

If  to  a  section  mounted  in  strong  alcohol  or  in  strong  glycerin 
is  added  a  little  water  by  allowing  it  to  run  under  the  cover-glass, 
it  will  be  found  after  a  short  time  that  solution  has  begun  to  take 
place,  and  the  radial  structure  may  then  be  seen  more  distinctly. 
The  masses,  in  fact,  are  made  up  of  delicate,  needle-like  crystals 
radiating  from  a  common  centre. 

To  another  section  of  the  same  material  let  there  be  added  a 
single  drop  of  10  per  cent,  solution  of  thymol  in  strong  alcohol, 
then,  after  a  few  minutes,  a  single  drop  of  strong  sulphuric  acid, 
the  object  then  be  covered,  and  the  slide  be  warmed  over  a  lamp- 
flame  :  the  crystals  will  have  dissolved  and  disappeared,  but  a 
red  color  will  have  been  produced  in  the  section,  showing  the 
presence  of  a  carbohydrate.  The  reaction  is  not,  however,  dis- 
tinctive of  iuulin,  since  any  other  soluble  carbohydrate  behaves 
in  the  same  way.  But  the  test  often  enables  one  to  distinguish 
between  sphere-crystals  of  inulin  and  similar  ones  of  other  sub- 
stances— for  example,  those  of  calcium  phosphate,  which  may  be 
associated  with  inulin  in  the  cells. 

II. — Let  attention  now  be  given  to  another  carbohydrate — 
namely,  sugar,  or,  rather,  to  the  sugars,  for  there  are  several  of 
them.  Objects  favorable  for  the  study  of  these  substances  are  the 
following:  the  stems  and  young  fruits  of  Maize  (Zea  Mays,  L.) ; 
the  stems  of  Sorghum  (Holchus  saccharatus,  L.)  •  the  stems  of 
Sugar-cane  (Saccharum  officinarum,  L.) ;  the  root  of  the  Sugar- 


STUDY   OF    INULIN    AND   SUGAR.  425 

beet  (Beta  vulgaris,  L.) ;  the  root  of  the  Sweet  Potato  (Convol- 
vulus batatas,  L.) ;  the  root  of  the  Carrot  (Daucus  Carota,  L.) ; 
the  fruit  of  the  Pear  (Pyrus  comnmnis,  L.)  •  the  fruit  of  the 
Apple  (Pyrus  Malus,  L.) ;  the  fruit  of  the  Musk-melon  (Cucu- 
mis  Melo,  L.) ;  the  fruit  of  the  Banana  (Musa  sapientum,  L.)  • 
and  the  fruit  of  the  Peach  (Amygdalus  persica,  L.). 

Let  a  peach  be  selected  for  the  first  experiment,  A  fruit  which 
is  fully  ripe,  but  not  yet  soft,  should  be  chosen,  and  the  sections 
need  not  be  very  thin.  One  of  them  is  placed  on  a  slide  and 
treated  first  with  the  10  per  cent,  solution  of  thymol  and  then 
with  a  drop  of  strong  sulphuric  acid,  as  was  done  in  the  study 
of  inulin.  The  result  is  the  same  except  that  the  red  color  ap- 
pears more  rapidly  and  without  the  application  of  heat.  The 
experiment  may  be  varied  by  applying  to  a  fresh  section  a  drop 
or  two  of  20  per  cent,  alcoholic  solution  of  a-naphthol,  and 
afterward  a  drop  of  strong  sulphuric  acid,  when  a  deep-violet 
color  will  rapidly  appear  in  and  around  the  section. 

Sections  of  any  of  the  other  objects  mentioned  in  the  above 
list  will  yield  similar  results ;  but,  since  sugar  is  more  abundant 
in  some  than  in  others,  the  color-reactions  will  differ  considerably 
in  intensity. 

These  reagents,  however,  do  not  enable  one  to  distinguish  be- 
tween the  different  kinds  of  sugars,  nor  even  to  tell  sugar  from 
some  other  carbohydrates,  without  a  good  deal  of  difficulty  ;  there- 
fore it  is  advisable  to  try  another  test. 

One  of  the  best  reagents  for  the  purpose  is  Fehling's  solution  (see 
Introduction).  Ten  cubic  centimetres  of  the  solution  are  heated 
to  boiling  in  an  evaporating-dish,  and  while  the  solution  is  still  at 
the  boiling  temperature  a  section  is  immersed  in  it  for  about  two 
seconds  and  then  withdrawn.  If  a  sugar  belonging  to  the  glucose 
group  be  present,  the  section  will  be  colored  by  an  ochrey-red 
deposit  of  copper  suboxide  in  the  tissues.  If  no  deposit  has 
taken  place  at  the  end  of  two  seconds,  but  a  red  one  does  occur 
after  boiling  for  a  longer  time,  it  may  be  concluded  that  a  sac- 
charose instead  of  a  glucose  is  present.  The  reason  why,  in  the 
latter  case,  the  suboxide  deposit  does  not  occur  at  once  is  because 
saccharose,  as  such,  is  not  capable  of  reducing  the  copper  from  its 
solution,  but  boiling  soon  changes  saccharose  into  invert-sugar, 
which  is  capable  of  producing  the  change. 


426  LABORATORY    EXERCISES   IN    BOTANY. 

If  even  after  long  boiling  no  red  deposit  takes  place,  iiiulin, 
maunite,  or  starch  may  be  present,  but  neither  glucose  nor  sac- 
charose sugars. 

The  common  Carrot  contains  cane-sugar,  and  a  section  of  this 
may  now  be  tested,  so  as  to  observe  the  difference  in  the  reaction 
between  the  two  sugar  groups. 


STUDY   OF   INULIN   AND   SUGAR. 


427 


PLATE  LXIV.— Cross-section  of  a  small  portion  of  the  Parenchymatous  Tissues  from  the 
inner  layer  of  the  bark  of  the  root  of  Chicory  (magnified  330  diameters).  The  root  had 
been  soaked  for  some  time  in  strong  alcohol  before  sectioning,  a,  a,  sphere-crystals  of 
inulin  in  an  intercellular  space ;  b,  a  smaller  crystal,  partially  disintegrated,  in  a  cell. 


EXERCISE  XIX. 

STUDY  OF  SECKETION-SACS. 

SECRETION-SACS  are  cells  which  at  maturity  have  lost  their 
protoplasm,  and  therefore  their  proper  cellular  character,  and  be- 
come filled  with  secreted  matters.  Their  forms  differ  in  different 
plants,  but  more  commonly  they  resemble  parenchyma-cells  in 
appearance  and  in  the  character  of  their  walls.  Sometimes, 
however,  they  are  much  elongated  and  might  be  mistaken  for 
laticiferous  tissue,  and  sometimes  their  walls  are  thickened  and 
more  or  less  lignified.  They  are  usually  classified,  according  to 
the  nature  of  their  contents,  into  resin-sacs,  mucilage-sacs,  crystal- 
sacs,  tannin-sacs,  etc.  Many  are  mixed  in  their  character,  contain- 
ing both  mucilage  and  crystals  or  both  resins  and  mucilage ;  or 
along  with  resinous  contents  there  may  be  tannic  or  alkaloidal 
principles. 

The  following  objects  afford  good  examples  of  the  principal 
groups : 

(1)  Resin-sacs:    the  rhizome    of   Ginger  (Zingiber  officinale, 
Eoscoe) ;  the  rhizome  of  Sweet  Flag  (Acorus  Calamus,  L.) ;  the 
bark  of  the  Sweet  Bay  (Magnolia  glauca,  L.)  ;  the  rhizome  of 
Bloodroot  (Sanguinaria  Canadensis,   L.);   and  the  stem  of  the 
Lizard's  Tail   (Saururus  ceriums,  L.). 

(2)  Mucilage-sacs:    the   root   of    the    Marsh  mallow    (Althaea 
officinalis,  L.) ;  the  bark   of   the  Slippery   Elm   (Ulmus  fulva, 
J//Wu-.) ;  and  the  bark  of  the  Basswood  (Tilia  Americana,  L.). 

(3)  Crystal-sacs:  the  root  of  Yellow  Dock  (Rumex  crispus,  L.) ; 
the  root  of  Rhubarb  (Rheum  officiuale,  Baillori) ;  the  root-bark 
of  the  Pomegranate  (Punica  Granatum,  L.) ;  and  the  bark  of 
Cascara  Sagrada  (Rhamnus  Purshiana,  DC.). 

(4)  Sacs  containing  crystals  and  mucilage :  the  bulb-scales  of 
the  Squill  (Scilla  maritima,  L.)  ;    the  bulb-scales  of   Amaryllis 
(Amaryllis  formosissima,  Willd.)-,  the  stems  of  the  Spiderwort 

429 


430  LABORATORY    EXERCISES    IN    BOTANY. 

(Tradescantia  Virgin  ica,  L.) ;  the  stems  of  the  Green  Dragon 
(Arissema  Dracoutium,  Schott.) ;  and  the  roofe  of  Orchis  (Orchis 
mascula,  L.). 

(5)  Tannin-sacs:  the  rhizome  of  Cranesbill  (Geranium  mac- 
ulatum,  L.)  and  the  stem  of  the  Horseshoe  Geranium  (Pelargo- 
nium zonale,  WiUd.). 

I. — Let  the  first  study  be  that  of  the  rhizome  of  Calamus. 
Either  the  fresh  rhizomes  or  the  dried  ones  to  be  had  in  apothe- 
cary shops  may  be  employed.  In  the  latter  case  the  material 
should  be  soaked  for  a  few  hours  in  water  before  sectioning. 

Let  both  a  transverse  and  a  longitudinal  section  be  mounted  in 
a  drop  of  water  and  be  examined  with  a  low  power.  The  tissues 
will  be  found  to  be  composed  largely  of  parenchyma,  which,  like 
that  of  the  Yellow  Water-lily,  is  very  loosely  arranged,  with  large 
and  rather  regular  intercellular  spaces.  Most  of  the  parenchyma- 
cells  contain  small  starch-grains  besides  protoplasm  and  a  nucleus, 
but  here  and  there  among  these  cells  are  others  of  considerably 
larger  size  and  rounded  in  outline,  in  whose  interior  neither  pro- 
toplasm nor  starch  is  discoverable,  but  which  contain  a  refractive 
liquid  sometimes  intermixed  with  brownish  solid  matter.  These 
cells  are  the  secretion-sacs. 

If  one  of  the  sections  now  be  treated  with  Russow's  potassium 
hydrate,  the  solid  matter  in  the  secretion- sacs,  which  before  was 
merely  brownish,  becomes  a  deep  red-brown,  while  the  walls  of 
the  sacs  are  more  sharply  defined.  Many  of  the  sacs,  it  will  be 
observed,  contain  none  of  the  brown  matter,  but  are  filled,  and 
often  strongly  distended,  with  the  transparent  refractive  liquid, 
which  shows  no  signs  of  saponification  even  after  long  immersion  in 
potash  solution.  It  may  be  concluded,  therefore,  that  this  liquid 
is  probably  a  volatile  oil.  This  conclusion  is  verified  by  treat- 
ing fresh  sections  respectively  with  alcannin  solution  and  with 
cyauin  solution.  Both  the  solid  and  the  liquid  contents  of  the 
secretion -sacs  become  strongly  stained  by  these  reagents.  The 
liquid,  therefore,  is  a  volatile  oil,  and  the  brownish  solid  matter 
is  a  resin.  Sometimes  the  latter  appears  to  be  crystalline;  more 
frequently  a  definite  structure  is  not  discernible. 

In  the  longitudinal  section  the  sacs  mostly  present  the  same 
appearance  as  in  the  transverse  section,  but  occasionally  one 
appears  slightly  elongated  or  ellipsoidal. 


STUDY   OF   SECRETION-SACS.  431 

II. — For  the  study  of  mucilage-sacs  let  a  series  of  cross-  and 
longitudinal  sections  of  the  root  of  the  Marsh  mallow  now  be 
made,  and  be  transferred  to  alcohol  until  required  for  use.  On 
placing  one  of  the  cross-sections  on  a  slide  in  a  drop  of  glycerin 
and  examining  it  with  the  low  power  the  mucilage-sacs  will  be 
seen  as  transparent  rounded  cells  rather  freely  but  irregularly 
scattered  through  a  smaller-celled  parenchyma  which  is  very  rich 
in  starch.  The  secretion-sacs  are  very  numerous  both  in  the  soft 
tissues  of  the  woody  zone — the  part,  that  is,  within  the  cambium 
zone — and  in  the  middle  and  inner  bark. 

If  to  a  fresh  section  a  drop  of  potassium-iodide  iodine  be 
applied,  the  contents  of  the  secretion-sacs  remain  unstained,  indi- 
cating that  no  proteids  are  present ;  but  if,  instead,  a  drop  of  the 
zinc-chloriodide  iodine  be  applied,  or  if  to  the  section  already 
stained  with  potassium-iodide  iodine  a  drop  of  sulphuric  acid  be 
added,  the  contents  will  acquire  a  deep-brown  color,  the  mucilage 
being  stained  by  these  reagents. 

The  contents  of  the  sacs  appear  nearly  homogeneous,  except 
that  sometimes  in  or  near  the  centre  of  the  sac  may  be  seen  a  few 
minute  dark  granules,  probably  mineral  in  their  character.  With 
good  illumination,  however,  there  may  be  observed  in  specimens 
treated  with  a  mixture  of  sulphuric  acid  2  parts  and  water  1  part, 
or  in  the  specimens  that  have  been  treated  with  the  iodine  and 
sulphuric  acid,  a  very  delicate  concentric  stratification  in  the 
mucilaginous  contents.  An  attempt  has  been  made  in  the  ac- 
companying drawing  (PI.  LXV.,  Fig.  2)  to  imitate  the  stratifi- 
cation-lines, but  they  are  much  more  numerous  and  delicate  than 
could  well  be  shown  in  a  drawing. 

The  walls  of  the  sacs,  like  those  of  the  adjacent  parenchyma- 
cells,  are  unstained  by  anilin  chloride  and  hydrochloric  acid,  but 
are  stained  blue  with  the  iodine  and  sulphuric  acid;  they  are 
therefore  composed  of  cellulose.  The  walls  have  also  about  the 
same  thickness  as  those  of  the  adjacent  parenchyma-cells. 

In  longitudinal  section  the  mucilage-sacs  usually  appear  some- 
what elongated,  but  seldom  attain  a  length  more  than  twice  as 
great  as  their  thickness.  They  may  be  regarded,  therefore,  as 
parenchyma-cells  whose  protoplasmic  contents  have  disappeared, 
giving  place  to  mucilage  which  has  come  to  occupy  the  whole 
interior  of  the  cells. 


432  LABORATORY    EXERCISES    IN    BOTANY. 

III.  Let  the  next  study  be  that  of  the  mucilage-  and  raphides- 
bearing  sacs  of  Arissema  Dracontium.  Having  cut  a  supply  of  sec- 
tions, transverse  and  longitudinal,  preferably  from  the  fresh  stem, 
one  of  each  kind  may  be  mounted  in  a  drop  of  water  and  be  ex- 
amined with  the  low  power.  In  the  cross-section,  among  the 
loosely-arranged  parenchyma-cells,  there  will  here  and  there  be 
seen  smaller  cells  with  dark,  apparently  minutely  granular  con- 
tents. These  cells  are  the  sacs  to  be  studied,  but  they  will  be 
understood  much  better  by  studying  the  longitudinal  section. 
Here  it  will  be  seen  that  the  sacs,  though  narrow,  are  often 
much  elongated — frequently  several  times  as  long  as  their  trans- 
verse diameter — though  short  ones  are  also  found;  and  the  solid 
matters  in  them,  which  in  the  transverse  section  appeared  gran- 
ular, is  here  seen  to  consist  of  great  numbers  of  long,  needle-like 
crystals  mostly  lying  parallel  to  each  other  and  to  the  length  of 
the  cells.  These  crystals  are  the  so-called  raphides. 

In  sections  cut  from  fresh  tissues  and  mounted  in  water  as  has 
been  directed  the  crystals  may  often  be  seen  shooting  out  through 
the  end  partitions  into  adjacent  cells.  This  is  caused  by  the 
mucilage  contained  in  the  sacs  along  with  the  crystals.  The 
mucilage  swells  by  the  imbibition  of  water  until  rupture  of  the 
end  walls,  which  are  weaker  than  the  lateral  ones,  takes  place, 
and  some  of  the  crystals  escape  with  the  escaping  mucilage. 

By  acetic  acid  the  crystals  are  not  attacked,  but  by  hydrochloric 
acid  they  slowly  disappear  without  effervescence ;  they  are  there- 
fore composed  of  calcium  oxalate. 

The  mucilage  is  stained  brownish  by  iodine  and  by  sulphuric 
acid,  but  not  so  strongly  as  is  the  mucilage  of  the  Marshmallow. 
It  stains  also  with  soda-corallin. 

IV. — The  tannins  are  abundant  aud  widely-distributed  sub- 
stances. They  occur  associated  with  other  matters — living  pro- 
toplasm, proteids,  starch,  etc — in  various  tissues,  but  sometimes 
cells  appear  to  be  especially  set  apart  as  containers  for  them. 
These  cells  are  called  tannin-sacs. 

If  sections  of  the  stem  of  Pelargonium  zonale  be  mounted  in 
a  drop  of  water  and  be  examined,  cells  will  be  seen  among  the 
starch-bearing  parenchyma-cells  of  the  pith  and  cortex,  which 
cells  are  filled  with  granular  matters,  but  contain  neither  starch 
nor  proteids.  These  cells  are  tannin-sac>,  for  if  to  a  fresh  section 


STUDY   OF   SECRETION-SACS.  433 

that  has  not  been  treated  with  water  a  drop  of  the  ferric-alum 
solution  be  applied,  a  blue-black  precipitate  will  immediately  be 
formed  in  them,  so  dense  in  its  character  as  to  render  the  sacs 
perfectly  opaque  even  after  the  sections  have  been  boiled  in 
carbolic  acid. 

These  secretion-sacs  are  precisely  similar  in  shape  and  in  the 
thickness  and  composition  of  their  walls  to  the  adjacent  paren- 
chyma-cells. In  fact,  many  of  the  parenchyma-cells  that  still 
contain  living  protoplasm  and  starch  are  shown  by  the  test  to 
contain  also  considerable  proportions  of  tannin.  The  blue-black 
color  may  also  be  seen  in  the  meristem-cells  of  the  cambium  zone, 
in  the  soft  bast-tissues  of  the  inner  bark,  and  even  to  a  limited 
extent  in  the  wood. 

In  studying  the  distribution  of  tannin  in  the  tissues,  of  course 
the  test-solution  should  be  applied  to  sections  that  have  not  been 
treated  with  water  or  with  any  other  tannin  solvent,  otherwise  the 
tannin  will  have  been  diffused  by  the  solvent  to  cells 'other  than 
those  in  which  it  was  secreted,  and  wrong  conclusions  may  be 
drawn.  The  best  results  are  obtained  by  mounting  the  section, 
dry,  on  a  slide  and  then  letting  the  ferric  solution  run  under  the 
cover-glass. 

If  to  another  section  a  drop  of  10  per  cent,  solution  of  pot- 
assium bichromate  be  applied  in  a  similar  manner,  there  will  be 
seen  in  the  tannin-containing  cells  a  dense  reddish-brown  pre- 
cipitate; if  to  still  another  section  a  little  of  a  solution  of  am- 
monium molybdate  in  an  aqueous  solution  of  ammonium  chloride 
be  applied,  there  will  be  seen  a  yellowish-brown  precipitate  in  the 
tannin-bearing  cells. 

There  are  a  few  other  substances  besides  the  tannins  that  pro- 
duce similar  precipitates  with  these  reagents,  but  if  in  any  case 
precipitates  of  the  color  above  described  be  attained  with  all  three 
of  these  reagents,  one  may  be  fairly  certain  that  the  precipitates 
are  due  to  the  presence  of  tannic  matters. 

If  permanent  preparations  are  desired,  thin  sections  which  have 
been  treated  with  the  ferric  solution  may  be  boiled  in  strong  car- 
bolic-acid solution  to  clear  them,  and  then  be  mounted  directly  in 
xylol  balsam. 

V. — In  Exercise  IV.,  in  which  was  studied  the  petiole  of  the 
Begonia,  there  were  observed  among  the  collenchyma-  and  paren- 

28 


434  LABORATORY    EXERCISES   IN    BOTANY. 

chyma-cells.sorae  cells  which  contained  stellate  masses  of  crystals 
which  by  suitable  tests  were  proved  to  be  composed  of  calcium 
oxalate.  Agglomerated  crystals  of  this  character  are  exceedingly 
common  in  plants.  Sometimes  they  are  associated  in  the  cells 
with  proteids,  starch,  etc.,  but  sometimes  they  occupy  the  cell- 
cavity  to  the  exclusion  of  other  matters. 

Accompanying  the  bast-fibres  in  the  bark  of  the  Slippery  Elm 
and  Locust  are  very  numerous  short  parenchyma-like  cells,  each 
usually  containing  a  crystal  of  calcium  oxalate.  The  crystals  are 
cliuorhombic,  and,  since  they  polarize  beautifully,  are  best  studied 
by  the  aid  of  polarized  light.  They  are  perhaps  the  commonest 
of  all  forms  of  plant-crystals. 

Specimens  for  study  by  polarized  light  are  best  prepared  by 
boiling  the  sections  in  carbolic  acid  to  clear  the  tissues  and  then 
mounting  them  in  balsam. 


STUDY    OF    SECRETIOX-SACS. 
b 


435 


PLATE  LXV.,  FIG.  1.— A  portion  of  Tissue  from  a  Transverse  Section  of  the  Rhizome  of 
Acorus  Calamus  (magnified  100  diameters) :  a,  o,  sacs  containing  volatile  oil  and  resinous 
matters ;  in  6,  6  the  contents  are  wholly  hyaline ;  c,  c,  ordinary  starch-bearing  paren- 
chyma-cells; d,  d,  intercellular  air-spaces. 

FIG.  2. — A  portion  of  Tissue  from  a  Transverse  Section  of  the  Root  of  the  Marshmallow 
(magnified  100  diameters) :  a,  a,  mucilage-sacs  (the  stratification  of  the  mucilage  after 
treatment  with  dilute  sulphuric  acid  is  indicated  by  dotted  circles) ;  6,  b,  medullary-ray 
cells ;  c,  c,  starch-bearing  parenchyma-cells.  The  drawing  was  made  from  the  central- 
cylinder  region  of  the  root. 


STUDY   OF   SECRETION-SACS. 


437 


PLATE  LXVI.— Small  portion  of  Longitudinal  Section  of  Stem  of  Green  Dragon  (mag- 
nified 100  diameters) :  a,  a,  parenchyma-cell  containing  protoplasm  and  minute  starch- 
grains  ;  6,  a  sac  containing  mucilage  and  numerous  raphides. 


EXERCISE  XX. 

STUDY  OF  INTERCELLULAR  AIR-SPACES  AND  SECRETION- 
RESERVOIRS. 

FOR  the  study  of  air-spaces  selections  may  be  made  from  the 
following  plants:  the  fragrant  White  Water-lily  (Nymphaa 
odorata,  Ait.),  the  Yellow  Water-lily  (Nnphar  advena,  Ait.),  the 
Bulrush  (Scirpus  lacustris,  L.)9  the  Indian  Turnip  (Arissema  tri- 
phyllum,  Torr.),  the  Bur-reed  (Sparganium  eurycarpum,  Engelm.), 
the  Pickerel-weed  (Pontederia  cordate,  L.),  the  Water  Plantain 
Alisma  Plantago,  L.),  the  Lizard's  Tail  (Saururus  ceriums,  L.), 
the  Arrow-leaf  (Sagittaria  variabilis,  Engelm.),  the  Carrot  (Daucus 
Carota,  L.),  the  Cow  Parsnip  (Heracleum  lanatum,  Michx.),  and 
the  Common  Parsnip  (Pastinaca  sativa,  L.).  The  most  conve- 
nient parts  to  employ  are  the  stems,  though  in  most  cases  the 
leaves  and  roots  also  afford  good  studies. 

For  the  study  of  secretion-reservoirs  the  following  are  rec- 
ommended :  the  roots  and  stems  of  the  Spikenard  (Aralia  race- 
niosa,  L.) ;  the  rhizomes  of  Wild  Sarsaparilla  (Aralia  nudicaulis, 
L.)  •  the  roots  of  Pellitory  (Anacyclus  Pyrethrtim,  DC.) ;  the 
young  fruits  of  the  Orange  (Citrus  Aurantium,  Risso) ;  the  stem 
of  the  Compass  Plant  (Silphium  laciniatum,  L.) ;  and  the  stems 
and  leaves  of  any  species  of  Pine  or  Fir. 

The  three  umbelliferous  plants  mentioned  in  the  former  list 
also  possess  secretion-reservoirs  which  are  good  for  study. 

Intercellular  air-spaces  exist  more  or  less  abundantly  in  nearly 
all  multicellular  plants,  and  they  probably  serve  the  important 
purpose  of  supplying  air  to  the  interior  tissues,  where  it  is  needed 
for  respiratory  purposes.  In  most  land-plants  these  air-spaces  are 
small  and  angular,  but  in  aquatics  they  are  usually  of  large  size 
and  often  have  very  regular  forms.  They  are,  moreover,  of  two 
kinds — those  formed  by  the  splitting  of  the  cell-wall  that  is  com- 
mon to  two  or  more  adjacent  cells,  and  those  formed  by  the  de- 
struction of  some  of  the  cells  of  a  tissue.  Those  produced  by  the 

439 


440  LABORATORY    EXERCISES    IN    BOTANY. 

former  mode  are  called  schizogenous ;  those  by  the  latter  mode, 
lysigenous. 

In  order  to  understand  schizogenous  spaces  it  must  be  known 
that  all  true  tissues  in  an  early  stage  of  their  development — that 
is,  when  they  are  in  the  form  of  meristem — are  destitute  of  inter- 
cellular spaces.  But  later  on,  as  the  tissues  develop,  owing  to  the 
weakening  by  chemical  change  which  takes  place  in  the  middle 
lamella,  and  to  the  strains  induced  by  the  rapid  development  and 
change  of  form  of  the  cells,  splitting  takes  place  at  the  points  of 
greatest  strain,  commonly  in  the  places  where  several  cells  come 
together.  The  separation  may  be  but  slight,  or  it  may  be  so  com- 
plete that  adjacent  cells  barely  touch  each  other  at  a  few  points  only. 

Secretion-reservoirs  and  intercellular  air-spaces  differ  from  each 
other  only  in  their  contents. 

I. — Attention  is  first  directed  to  the  air-spaces  in  the  petiole  of 
the  Yellow  Water-lily.  Either  fresh  or  alcoholic  material  may 
be  employed.  Having  made  several  sections,  longitudinal  and 
transverse,  one  of  each  kind  is  mounted  in  water  on  a  slide  and  is 
examined  with  the  low  power.  Beneath  the  small-celled  epider- 
mis and  the  collenchyma  is  a  larger-celled  parenchyma  in  which 
there  are  next  the  outside  rather  small  spaces ;  farther  interior 
these  spaces  become  increasingly  large,  until  a  millimetre  or  so 
beneath  the  surface  they  have  many  times  the  diameter  of  the 
cells  which  bound  them.  They  are,  moreover,  quite  regular  in 
form,  often  pentagonal. 

At  the  angles  the  boundary-cells  are  relatively  considerably 
larger  than  those  on  the  sides;  they  are  longer  also  in  the  longi- 
tudinal section,  and  at  considerable  intervals  in  the  column  of  cells 
constituting  one  of  these  angles  there  occurs  a  cell  of  altogether  dif- 
ferent shape — a  freely-branching  one  that  sends  its  branches  into 
the  three  or  four  adjacent  spaces.  These  peculiar  branching  cells 
are  called  trichoblasts.  They  sometimes  occur  in  other  aquatics 
besides  the  Water-lily  family — in  the  genus  Limnanthemum,  for 
example,  and  in  some  Araceae.  It  will  be  observed  that  these 
cells  are  thicker-walled  than  are  the  adjacent  parenchyma-cella, 
and  that  their  walls  are  roughened  by  numerous  very  minute 
crystals  said  by  Hugo  von  Mohl  to  be  crystals  of  calcium  oxalatc  ; 
but  this  is  doubtful,  as  they  remain  apparently  unchanged  after 
boiling  with  strong  hydrochloric  acid.  To  see  their  crystalline 


STUDY    OF    INTERCELLULAR    AIR-SPACES,    ETC.  441 

forms  distinctly  requires  the  use  of  a  very  high  power.  It  is 
difficult  to  surmise  what  can  be  the  use  of  these  trichoblasts. 

Removing  now  the  cover-glass,  applying  one  or  two  drops 
of  anilin  chloride,  after  a  few  moments  as  much  hydrochloric 
acid,  and  again  examining,  it  is  found  that  the  trichoblasts  have 
acquired  a  deep-yellow  color  which  proves  them  to  be  strongly 
lignified ;  in  fact,  they  are  about  the  only  lignified  tissue  present, 
even  the  depauperated  vasal  bundles  showing  little  if  any  ligui- 
fication. 

By  comparing  the  longitudinal  and  the  transverse  sections  it  will 
be  seen  that  the  large  intercellular  spaces  form  regular  channels 
extending  long  distances  through  the  petiole  or  stem,  only  inter- 
rupted here  and  there  by  loose  masses  of  branching  cells.  These 
cells,  like  the  trichoblasts,  are  really  a  kind  of  internal  hair,  but, 
unlike  the  latter,  are  not  lignified.  They  originate  in  a  little  sac- 
like  outgrowth  from  one  of  the  cells  in  the  wall  of  the  passage. 
The  sac  elongates  and  branches  profusely,  and  the  branches  are 
broken  up  into  cells  by  the  formation  of  transverse  partitions. 
In  favorable  longitudinal  sections  the  masses  may  be  seen  attached 
by  the  base  to  the  wall  of  the  passage.  The  walls  of  these  hair- 
cells,  it  will  be  observed,  are  very  thin,  and  it  is  possible  that 
they  are  of  service  to  the  plant  in  absorbing  gaseous  food-mate- 
rial from  the  air-passages. 

The  air-passages  in  the  petiole  are  in  communication  with  those 
in  the  rhizome  on  the  one  hand,  and  with  those  of  the  leaf  and 
with  the  stomata  on  the  upper  surface  of  the  latter  on  the  other, 
so  that  they  constitute  a  complete  system  of  aerating  channels 
throughout  the  plant. 

II. — For  the  study  of  secretion-reservoirs  the  rhizome  of  Ara- 
lia  imdicaulis  is  selected. 

Focusing  upon  a  transverse  section  mounted  in  a  drop  of  water, 
there  are  seen  in  the  middle  layer  of  the  bark  numerous  rather 
large  spaces  resembling  a  good  deal  those  of  Nuphar,  just  studied. 
But  if  the  section  is  of  a  fresh  stem,  there  will  be  seen  clinging 
to  the  wall  of  the  passage  some  refractive  droplets  which  are  rem- 
nants of  the  liquid  that  in  the  living  plant  filled  the  reservoir. 

It  will  be  seen,  furthermore,  that  the  cells  immediately  sur- 
mnding  the  reservoir  are  smaller  in  size  and  more  densely  gran- 
ular in  their  contents  than  those  a  little  farther  removed.  They 


442  LABORATORY    EXERCISES   IN   BOTANY. 

are  the  secreting  cells,  and  the  liquid  which  they  secrete  is  dis- 
charged, by  some  means  not  yet  well  understood,  into  the  reser- 
voir where  it  accumulates.  The  contents  of  these  reservoirs  dif- 
fer widely  in  different  plants  :  in  some  they  are  mucilaginous,  in 
others  oleo-resinous,  and  in  still  others  there  may  be  a  milk- 
like  emulsion  consisting  of  a  mixture  of  resinous  and  muci- 
laginous matters.  In  the  present  instance  the  transparency  and 
fluidity  point  to  the  presence  of  an  oleo-resin  ;  this  conclusion 
may  be  confirmed  by  an  application  of  the  alcanuin  and  cyan  in 
tests.  These  tests  would  better  be  applied  to  the  fresh  sections, 
and  to  longitudinal  sections  in  preference  to  transverse  ones,  for 
the  very  fluid  oleo-resin  too  readily  escapes  from  the  reservoirs 
in  the  transverse  section. 

A  careful  study  of  the  longitudinal  section,  particularly  of  one 
that  has  been  treated  with  the  alcaunin  solution  in  order  that  the 
reservoirs  may  easily  be  traced,  shows  that  the  reservoirs  are  cylin- 
drical, unbranched,  nearly  straight,  and  that  they  extend  long  dis- 
tances in  the  direction  of  the  length  of  the  rhizome. 

The  young  and  growing  above-ground  stem  affords  an  oppor- 
tunity to  study  the  development  of  this  type  of  intercellular 
space,  the  schizogenous.  A  cross-section  of  such  a  stem  will 
show  clusters  of  three  or  four  granular  cells  about  a  small  inter- 
cellular space.  Lower  down  in  the  stem,  a  similar  section  will 
show  clusters  of  a  like  character  except  that  the  number  of 
granular  cells  is  larger  and  the  space  they  enclose  is  also  larger. 
The  three  or  four  cells  with  which  the  development  began  have 
increased,  mostly  by  radial  division,  to  a  considerable  number. 
This  is  the  usual  method  of  development  of  reservoirs  of  this  class. 

The  air-spaces  of  Nuphar  are  also  of  the  schizogenous  variety. 

If  sections  be  made  of  the  rind  of  the  immature  fruit  of  the 
Orange,  lysigeuous  reservoirs  will  be  seen  in  different  stages  of 
development.  In  the  earlier  stage  there  is  only  a  small  cluster 
of  granular  cells  ;  in  a  little  later  one,  a  larger  cluster,  with  indi- 
cations that  the  central  cells  are  undergoing  disintegration;  and 
in  a  still  later  one  the  central  cells  have  disappeared  and  a  drop 
of  oil  occupies  their  place.  This  area  of  disintegrating  cells  con- 
taining the  oil-globule  is  surrounded  by  layers  of  secret  inir  cells, 
some  of  which  may  in  turn  break  down  and  so  increase  the  si/c 
of  the  oil-cavity. 


STUDY   OF   INTERCELLULAR   AIR-SPACES,    ETC.  443 


jATE  LXVIL,  FIG.  1.— Transverse  Section  of  Petiole  of  Nuphar  advena  (magnified  65 
iameters) :  a,  epidermis ;  b,  collenchyma ;  c,  c,  c,  c,  intercellular  air-spaces ;  d,  part  of 
vasal  bundle ;  e,  e,  trichoblasts. 

FIG.  2.— Longitudinal  Section  of  the  same  (magnified  65  diameters),  showing  some  of 
the  air-spaces  cut  through  lengthwise,  and  so  appearing  trough-like :  a,  a,  air-spaces ;  &, 
a  trichoblast  with  its  branches  projecting  into  air-spaces  on  either  side. 


STUDY   OF   INTERCELLULAR   AIR-SPACES,    ETC.  445 


PLATE  LXVIIL— Small  portion  of  Transverse  Section  of  Middle  Bark  of  the  Rhizome 
of  Aralia  nudicaulis  (magnified  about  300  diameters) :  a,  secretion-reservoir ;  b,  one  of 
the  secretion-cells  bounding  the  reservoir;  c,  c,  intercellular  air-spaces. 


EXERCISE  XXI. 

STUDY  OF   VASAL   BUNDLES:    THE   CONCENTKIC   BUNDLE. 

VASAL  bundles,  or,  as  they  are  often  called,  "  fibre- vascu- 
lar bundles,"  constitute  the  tough,  stringy  tissues  of  plants. 
The  harder  portions  of  most  stems  and  roots,  and  the  frame- 
work of  veins  in  leaves,  consist  chiefly  of  vasal  bundles.  They 
are  pre-eminently  the  strengthening  and  conducting  portions  of 
the  plant  structure.  A  vasal  bundle  is  usually  made  up  of  a 
considerable  variety  of  tissues,  and  these  are  arranged  in  two 
groups  which  differ  from  each  other  quite  widely  in  the  charac- 
ter of  their  elements.  One  group  is  called  xylem  and  the  other 
is  called  phloem.  Some  bundles  are  composed  of  one  of  each  of 
these  groups ;  others,  of  two  or  more  strands  of  phloem  or  of 
xylem  or  of  both.  The  bundle  may  or  may  not  be  marked  off 
from  the  surrounding  tissues  by  a  distinct  layer  of  cells  called  the 
bundle-sheath  or  endodermis.  Both  phloem  and  xylem  usually 
contain  a  variety  of  tissues,  but  different  plants,  as  well  as  dif- 
ferent parts  of  the  same  plant,  differ  as  to  the  number  of  kinds 
in  each.  The  essential  tissue  of  the  xylem,  however,  is  tracheary 
tissue  (which  may  include  either  tracheids  or  ducts  or  both),  and 
that  of  phloem  is  sieve-tissue.  Accompanying  the  tracheary  tissue 
in  the  xylem  are  often  found  wood-cells  and  wood  parenchyma- 
cells,  ordinary  parenchyma-cells,  and  sometimes  secretion-cells  of 
various  sorts ;  and  associated  with  the  sieve-tissues  in  the  phloem 
are  usually  companion-cells,  often  ordinary  parenchyma  and  bast- 
fibres,  and  sometimes  secretion-cells  and  laticiferous  tissues. 

Vasal  bundles  are  classified  according  to  the  relative  arrange- 
ment of  the  phloem  and  xylem  masses  or  strands.  Three  differ- 
ent types  are  recognized — the  concentric,  the  collateral,  and  the 
radial. 

In  the  concentric  type  one  of  the  elements,  either  phloem  or 
xylem,  occupies  a  central  position  and  is  surrounded  by  the  other; 
there  are  hence  two  varieties — the  one  in  which  the  xylem  is  cen- 

447 


448 


LABORATORY   EXERCISES    IN    BOTANY. 


tral  and  the  phloem  forms  a  cylinder  which  surrounds  it,  and  the 
other  in  which  the  phloem  is  central,  surrounded  by  the  xylein. 

In  the  collateral  type  the  phloem  and  the  xylem  are  located  side 
by  side.  There  are  three  varieties:  the  closed  collateral,  in  which 
there  is  no  meristem  or  cambium  between  the  phloem  and  the 
xv It'in  ;  the  open  collateral,  in  which  there  is  a  meristem-layer 
between  the  two  elements  ;  and  the  bi-col lateral,  in  which  then- 
are  two  phloem  masses  with  a  xylein  mass  lying  between  them. 
Such  a  bundle  is  usually  open  on  one  or  both  sides ;  that  is, 
between  the  xylem  and  one  or  both  of  the  phloem  masses  is 
meristem-tissue. 

In  the  radial  type  the  xylem  is  arranged  in  the  form  of  rays, 
or  like  the  spokes  of  a  wheel,  and  the  phloem  masses  lie  between 
the  xylem-rays,  usually  well  toward  the  exterior  of  the  bundle. 

The  folio  wing  diagrams  will  show  at  a  glance  the  relative  arrange- 
ment of  phloem  and  xylem  in  the  different  bundles,  and  also  the 
position  of  the  meristem-layer  in  those  bundles  which  possess  one. 


DBF 

FIG.  7.— A,  Concentric  bundle  with  the  xylem  interior  ;  B,  concentric  bundle  with  the 
xylem  exterior ;  C,  closed  collateral  bundle ;  D,  open  collateral  bundle;  E,  bi-collaU-ral 
bundle  ;  F,  radial  bundle  (p,  phloem ;  x,  xylem ;  m,  meristem). 

Let  this  exercise  be  devoted  to  the  study  of  concentric  bundles. 
Good  examples  for  study  may  be  found  in  the  stem  or  the  petiole 
of  almost  any  common  fern,  as,  for  example,  the  Common  Brake 
(Pteris  aquilina,  L.\  the  'Marginal  Shield-fern  (Aspidium  inar- 
ginale,  X/rwte),  the  Male  Fern  (Aspidium  Filix-mas,  Ximrtz\ 
and  the  Common  Polypody  (Polypodium  vnlgarc,  L.) ;  in  the 
steins  of  the  Sj'lagincllas,  as  Selaginelhi  rupestris,  Sj»rii(/.  ;  and 
in  the  rlii/omes  of  the  Hlne  Flag  (Iris  versicolor,  L.),  the  False 


STUDY    OF   VASAL    BUNDLES.  449 

Solomon's  Seal  (Smilacina  racemosa,  Desf.),  and  the  Sweet  Flag 
(Acorus  Calamus,  L.). 

I. — Attention  is  first  directed  to  that  form  of  the  bundle  in 
which  the  xylem  is  surrounded  by  the  phloem.  Sections,  trans- 
verse and  longitudinal,  are  made  of  the  rhizome  of  Pteris  aquilina, 
care  being  taken  that  the  longitudinal  section  cuts  through  one  of 
the  bundles  as  nearly  in  the  centre  as  possible,  and  preferably  in 
the  direction  of  its  greatest  width.  The  section  will  then  show  all 
of  the  different  tissues  of  the  bundle. 

A  thin  transverse  section  is  first  placed  upon  a  slide  and  treated 
with  the  phlorogluciu  reagent,  which  stains  most  of  the  xylem- 
tissues  red,  but  leaves  the  phloem  wholly  unstained.  The  bundles 
are  then  easily  recognized,  and  it  will  be  seen  that  the  rhizome 
contains  a  single  circle  of  them,  and  within  the  circle,  near  its 
centre,  two  or  three  larger  and  considerably  elongated  bundles 
lying  between  two  elongated  masses  of  dark-colored  sclerenchyma- 
fibres.  It  will  be  seen  further  that,  while  the  bundles  differ  in 
size  and  in  shape,  they  agree  substantially  in  the  arrangement  of 
their  parts :  the  red-stained  ducts  of  the  xylem  are  in  the  centre ; 
around  them  is  an  area  of  soft  tissues — the  phloem  ;  and  sepa- 
rating the  bundle  sharply  from  the  fundamental  tissues  exterior 
to  it  is  a  single  layer  of  peculiar  cells  constituting  the  bundle- 
sheath  or  endodermis. 

It  has  already  been  learned  (Exercise  XI.)  that  scalariform 
ducts  abound  in  the  xylem  ;  in  fact,  this  portion  of  the  bundles 
is  almost  wholly  composed  of  them.  The  only  exceptions  are  a 
few  spiral  ducts  at  or  near  the  ends  of  the  more  or  less  elongated 
xylem  mass,  or  sometimes  only  at  one  of  the  ends,  and  a  few 
small  starch-bearing  parenchyma-cells  near  the  centre.  All  but 
the  latter  are  strongly  reddened  by  the  phloroglucin  reagent. 

In  order  that  the  phloem  portion  of  the  bundle  may  be  studied 
satisfactorily  another  preparation  should  be  made  of  both  the 
transverse  and  longitudinal  sections.  The  sections  should  be 
treated  with  chloral-hydrate  iodine,  so  that  the  thinner  cell-walls 
may  be  seen  distinctly  and  the  finer  starch-grains  be  recognized. 
In  contact  with  the  xylem,  on  its  exterior,  will  be  seen  one  or  two 
tiers  of  small  parenchyma-cells  containing  fine-grained  starch. 
Immediately  exterior  to  these  are  cells  averaging  larger  in  calibre 
and  containing  no  starch,  but  rich  in  albuminous  matters ;  though 


LABORATORY    EXERCISES   IN    BOTANY. 

it  is  not  an  easy  thing  to  detect  any  sieve-plates,  these  are  the 
sieve-elements.  The  sieve-tissues  are  associated  with  elongated, 
slender,  almost  fibrous,  but  uulignified  companion-cells,  rich  in  pro- 
toplasm, but  not  containing  starch.  These  cells  are  most  abun- 
dant immediately  exterior  to  the  sieve-elements.  Still  farther 
exterior,  and  immediately  interior  to  the  endodermis,  is  a  layer 
of  somewhat  elongated  parenchyma-cells,  of  rather  larger  calibre 
than  the  other  parenchyma-cells  in  the  phloem  area.  They  are 
very  rich  in  small-sized  starch-grains. 

The  endodermis,  which  sharply  limits  the  bundle  on  the  out- 
side, is  composed  of  long,  prismatic,  rather  thin-walled  cells 
which  in  transverse  section  appear  somewhat  lengthened  taugen- 
tially.  Their  radial  walls  are  marked  with  a  dark  streak  and  are 
much  more  fragile  than  the  other  portions  of  the  walls,  so  that 
often  they  are  ruptured  clear  around  the  bundle  in  cutting  a  sec- 
tion. The  endodermis  when  old  has  its  walls  usually  more  or 
less  cutinized,  and  in  the  radial  walls  a  little  red  color  is  devel- 
oped by  the  phloroglucin  reagent. 

Exterior  to  the  endodermis  are  the  relatively  large  parenchyma- 
cells,  rich  in  large-sized  starch-grains. 

II. — For  the  study  of  concentric  bundles  in  which  the  xylem 
is  exterior,  let  a  series  of  sections,  longitudinal  and  transverse, 
now  be  made  of  the  rhizome  of  Smilacina  racemosa. 

The  same  methods  may  be  employed  as  in  the  preceding  study, 
or,  if  permanent  preparations  are  desired,  the  gentian-violet  and 
eosin  process  will  give  admirable  results.  The  sections,  made 
from  material  which  has  been  fixed  by  means  of  alcohol  or  acetic 
alcohol,  are  first  washed  if  the  latter  reagent  has  been  employed, 
then  stained  with  anilin- water  gentian-violet,  then  washed,  first 
in  ordinary  alcohol  and  afterward  in  absolute  alcohol,  then  placed 
in  eosin  oil  of  cloves  for  a  few  minutes,  and  lastly  mounted  in 
xylol  balsam. 

As  in  the  fern,  the  tracheary  elements  of  the  xylem  stain  with 
the  phloroglucin  and  anilin-chloride  reagents,  while  the  phloem 
elements  do  not ;  but  here,  in  most  of  the  bundles  at  least,  the 
former  are  arranged  in  a  zone  about  the  latter.  In  a  few  in- 
stances, however,  bundles  occur  in  which  the  xylem  ring  is  in- 
complete; that  is,  it  is  interrupted  at  one  point  by  soft  tissues 
allied  to  those  of  the  phloem  part  of  the  bundle.  Such  a  bundle 


STUDY   OF   VASAL   BUNDLES. 


451 


might  be  regarded  as  a  closed  collateral  bundle  in  which  the 
xylem  has  Dearly  enclosed  the  phloem.  In  fact,  since  closed 
collateral  bundles  are  much  the  more  common  in  the  stems  of 
mouocotyls,  and  since  in  some  monocotyls  they  are  found  associ- 
ated with  concentric  bundles  which  have  a  central  phloem,  there 
are  good  reasons  for  regarding  the  latter  as  only  a  modification  of 
the  former. 

Another  difference  between  the  bundle  with  a  central  phloem 
and  the  other  type  of  concentric  bundle  is  the  fact  that  there  is  no 
endodermis  to  separate  the  bundle  from  adjacent  tissues.  The 
parenchyma-cells  in  contact  with  the  xylem  elements  are  only 
a  little  smaller  than  the  ordinary  parenchyma-cells  of  the  stem. 

The  longitudinal  section  shows  that  the  xylem  consists  almost, 
wholly  of  tracheids  with  small  bordered  pits,  that  the  phloem 
consists  of  thin-walled  sieve-tubes  with  very  oblique  plates,  and 
that  the  sieve-tubes  are  associated  with  long  parenchyma-cells  rich 
in  protoplasm  and  containing  greatly  elongated  fusiform  nuclei. 

In  the  great  majority  of  bundles  having  a  central  phloem  the 
structure  is  substantially  the  same  as  that  observed  in  the  example 
just  studied.  This  variety  seldom  if  ever  occurs  elsewhere  than 
in  the  stems  and  leaves  of  some  monocotyls.  Concentric  bundles 
of  the  other  type — that,  namely,  in  which  the  phloem  is  exterior 
— are  the  kind  characteristic  of  the  stems  and  leaves  of  nearly  all 
ferns.  Only  in  rare  instances  are  they  found  in  cycads  and  dicotyls. 


STUDY   OF    VASAL    BUNDLES. 


453 


PLATE  LXIX.— One  of  the  smaller  Concentric  Bundles  in  the  Rhizome  of  Pteris 
aquilina  (magnified  330  diameters) :  a,  a,  a,  cells  of  the  endodermis ;  b,  cell  of  starch- 
bearing  parenchyma  from  the  layer  of  cells  immediately  beneath  the  endodermis  ;  c,  c,  c, 
sieve  elements  ;  d,  d,  spiral  ducts  at  one  end  of  the  xylem  mass ;  e,  c,  e,  scalariform  ducts 
in  the  xylem ;  /,  parenchyma-cell  in  interior  of  xylem  mass ;  g,  parenchyma-cell  from 
fundamental  tissues  exterior  to  the  bundle,  containing  large  starch-grains. 


STUDY   OF   VASAL   BUNDLES. 


455 


PLATE  LXX.— A  Concentric  Bundle  drawn  from  Transverse  Section  of  Rhizome  of 
Smilacina  racernosa  (magnified  330  diameters) :  a,  a,  parenchyma-cells  exterior  to  bundle  ; 
6,  6,  pitted  tracheids  of  xylem ;  c,  c,  sieve  elements  of  phloem ;  d,  an  opening  in  the  xylei 
ring. 


EXERCISE  XXII. 

STUDY   OF   COLLATERAL  BUNDLES. 

COLLATERAL  bundles  occur  in  the  stems  and  leaves  of  a  few 
ferns,  including  the  genera  Ophioglossum  and  Osmunda,  and  in 
the  stems  of  the  Equisitacese,  but  with  these  exceptions  are  con- 
fined to  the  stems  and  leaves  of  phanerogams,  of  which  they  are 
characteristic. 

In  the  ferns  mentioned,  in  the  Equisetacese,  and  in  monocotyls 
the  bundles  are  usually  closed ;  in  dicotyls  they  are  usually  open. 
In  the  great  majority  of  dicotyls  the  open  bundles  are  of  the  sort 
which  consists  of  one  xylem  and  one  phloem  strand,  but  a  few,  as 
the  members  of  the  natural  order  Cucurbitacese,  are  of  the  bi- 
col lateral  variety. 

Convenient  plants  for  the  study  of  closed  bundles  are  the 
following  :  the  Greenbrier  (Smilax  rotundifolia,  L.),  the  Spider- 
wort  (Tradescantia  Virginica,  L.\  the  Corn  (Zea  Mays,  L.),  the 
Bulrush  (Scirpus  lacustris,  i.),  the  Water  Plantain  (Alisma  Plan- 
tago,  L.),  the  Arrow-head  (Sagittaria  variabilis,  Engelm.\  and  the 
Yellow  Nelumbo  (Nelumbo  lutea,  Pers.). 

Good  plants  for  the  study  of  open  bundles  are  the  Yellow 
Parilla  (Menispermum  Canadense,  L.),  the  Virgin's  Bower  (Cle- 
matis Virginiana,  £.),  the  Dutchman's  Pipe  (Aristolochia  Sipho, 
UHer.\  the  Sycamore  (Platan us  occidentals,  £.),  the  Bittersweet 
Solanum  Dulcamara,  L.\  the  Lizard's  Tail  (Saururus  cernuus,  L.), 
and  the  Bass  wood  (Tilia  Americana,  L.). 

For  bi -collateral  bundles  the  following  plants  are  excellent :  the 
Pumpkin  (Cucurbita  Pepo,  L.\  the  Squash  (Cucurbita  maxima, 
Duchesne),  and  the  Wild  Cucumber  (Echinocystis  lobata,  Torr. 
and  Gray). 

I. — For  the  study  of  a  closed  bundle  let  sections  be  made  of 
the  stem  of  Tradescantia  Virginica.  On  staining  a  cross-section 
with  the  phloroglucin  or  the  aniliu-chloride  reagent  the  bundles 
are  readily  recognized,  and  they  are  seen  to  be  scattered  without 

457 


458  LABORATORY    EXERCISES    IN    BOTANY. 

any  definite  order  through  the  stem.  The  bulk  of  the  stem  is 
made  up  of  large-celled  parenchyma  rich  in  starch-grains,  while 
the  bundles  and  the  sheath  which  encloses  each  of  them  are  com- 
posed of  cells  of  rather  small  diameter,  containing  either  ii in- 
grained starch  or  none  at  all. 

The  bundle-sheath,  or  endodermis,  is  composed  of  a  single 
layer  of  cells  which  in  transverse  section  look  much  like  ordi- 
nary parenchyma-cells  except  that  they  are  smaller,  but  in  longi- 
tudinal view  are  observed  to  be  considerably  longer.  They  arc 
also  destitute  of  starch,  and  they  show  no  cutiuizatiou.  In  fact, 
in  collateral  bundles  generally,  when  an  endodermis  is  present  at 
all,  it  is  less  sharply  defined  than  in  concentric  and  radial  bundles. 
It  is  more  frequently  wanting  altogether. 

The  xylem  in  many  of  the  bundles  forms  a  V-shaped  mass  con- 
sisting almost  wholly  of  annular  and  spiral  ducts,  but  in  some 
instances  the  row  of  ducts  forms  a  complete  circle  about  the 
phloem.  Indeed,  in  this  plant  the  relationship  between  the 
closed  collateral  bundle  and  that  form  of  the  concentric  one  in 
which  the  phloem  is  enclosed  by  the  xylem  is  clearly  shown. 

Just  within  the  endodermis,  at  the  vertex  of  the  V-shaped  xylem 
mass  or  in  the  corresponding  part  of  the  concentric  bundles,  is 
usually  found  an  intercellular  space  of  considerable  size.  This  is 
common  in  closed  collateral  bundles.  At  this  end  of  the  bundle  are 
the  oldest  portions  of  the  xylem,  and  in  many  monocotyls  when 
the  bundles  are  mature  it  is  found  that  the  ducts  next  this  portion 
have  split  away  from  their  companions  and  lie  loose  in  the  inter- 
cellular space.  This  seldom  occurs,  however,  in  Tradescantia. 

The  phloem  portion  of  the  bundle  consists  almost  wholly  of 
sieve-cells  of  the  ordinary  form  and  of  cambiform  or  companion- 
cells  with  lengthened  nuclei. 

II. — For  the  study  of  an  open  collateral  bundle  let  section.-  IK? 
made  of  the  stem  of  Saururus  ceruuus,  some  time  before  the  plant's 
blossoming  season  is  over.  It  is  well,  in  order  to  distinguish  the 
parts  clearly,  that  one  set  be  treated  either  with  the  anil  in-chloride 
or  with  the  phloroglucin  reagent,  and  another  with  the  chloral- 
hydrate  iodine  solution.  If  the  bundle  be  nearly  mature  and  from 
an  above-ground  stem,  it  will  be  separated  from  the  surrounding 
loosely-arranged  parenchyma  l»y  a  .-heath  composed  of  several 
layers  of  thick-walled  sclerenchy ma-fibres.  The  cells  composing 


STUDY   OF   COLLATERAL   BUNDLES.  459 

this  fibrous  sheath  are  not  all  alike.  Those  facing  outward  in  the 
stem  and  bordering  the  soft  bast-elements  on  the  exterior  side  of 
the  bundle,  being  thicker-walled  than  the  rest  and  constituting  a 
thicker  mass,  are  the  bast-fibres,  and  those  at  the  opposite  or  xylera 
end  of  the  bundle,  being  developed  into  somewhat  thinner-walled 
cells,  are  to  be  regarded  as  wood-cells.  The  thick-walled  cells  of 
the  sheath  which  lie  on  the  radial  faces  of  the  bundle  and  connect 
the  bast-fibres  with  the  wood-cells  average  of  larger  diameter,  are 
somewhat  thinner- walled,  and  possess  fewer  pore-canals  than  the 
cells  composing  the  rest  of  the  sheath.  They  are  also  less  elon- 
gated when  viewed  in  longitudinal  section.  In  the  bundles  of  the 
rhizome  the  structure  is  similar  except  that  this  portion  of  the 
sheath  is  composed  of  cells  whose  walls  have  not  undergone  the 
lignified  thickening  at  all,  lignified  fibres  occurring  only  at  the 
outer  and  inner  ends  of  the  bundle. 

The  xylem,  aside  from  the  wood-cells  mentioned,  which  may  be 
accounted  a  part  of  it,  is  composed  of  elongated  parenchymatous 
cells  (wood-parenchyma),  secretion-cells,  and  tracheary  tissues. 
The  latter  consist  of  a  few  conspicuous  scalariform  ducts  in  the 
outer  and  later-formed  portion  of  the  xylem,  and  of  smaller 
annular  and  spiral  ducts  in  the  inner  and  older  portion. 

The  phloem  consists  of  the  bast-fibres  already  mentioned  and 
of  sieve-  and  companion-cells  mixed  with  which  are  a  few  elon- 
gated secretion-cells.  The  secretion-cells  are  best  seen  in  sections 
which  have  been  stained  either  with  the  alcannin  solution  or  with 
an  aqueous  solution  of  Bismarck  brown. 

At  the  junction  of  the  phloem  and  the  xylem  are  several  tiers 
of  tangentially  lengthened,  small,  and  thin-walled  cells  which  are 
mostly  arranged  in  distinct  radial  rows.  Like  the  adjacent  ele- 
ments, they  are  lengthened  in  the  direction  of  the  longest  diam- 
eter of  the  stem.  These  cells  constitute  the  meristem-  or  cam- 
bium-tissue. This,  as  has  already  been  stated,  is  not,  in  the  strict 
sense  of  the  term,  a  distinct  tissue,  but  rather  is  made  up  of  young 
cells  not  yet  developed  into  tissues,  some  of  the  cells  destined  to 
form  one  kind  of  tissue,  others  another. 

Meristem  always  consists  of  very  thin-walled  cells,  rich  in 
protoplasm,  with  walls  of  cellulose,  and  without  intercellular 
spaces.  The  cells  are  also,  until  the  vegetative  work  of  the 
plant  is  completed,  in  a  state  of  active  division. 


460  LABORATORY    EXERCISES    IX    BOTANY. 

The  stem  of  Saururus  is  herbaceous  and  dies  down  at  the  close 
of  the  season  of  growth,  and  although  the  activity  of  the  cam- 
bium continues  until  flowering,  it  soon  after  ceases,  and  the 
bundles,  before  the  death  of  the  stem,  become  closed.  In  the 
stems  of  dicotyl  shrubs  and  trees,  however,  the  stoppage  of 
growth  in  the  cambium  zone  is  only  temporary ;  in  the  spring 
activity  is  resumed,  and  so  the  bundles  increase  in  length  in  a 
radial  direction  year  by  year. 

III. — For  the  study  of  bi-collateral  bundles  let  sections  be 
made  of  the  stem  of  Cucurbita  Pepo,  thirty  or  forty  centimetres 
back  of  its  apex,  where  the  bundles  will  be  found  fairly  mature. 

The  xylem  portion  of  the  bundle  is  easily  recogni/ed  by  the 
very  large  ducts  which  occupy  its  outer  four-fifths  or  more.  These 
ducts  have  already  been  studied  (see  Exercise  XI.).  In  the  inte- 
rior portion  of  the  xylem — that  is,  in  that  portion  which  faces 
toward  the  centre  of  the  stem — which  is  also  the  first-formed 
portion,  are  a  number  of  scattered  ducts  of  much  smaller  sixe, 
which  are  mostly  spiral  and  annular.  The  tissue  which,  in  the 
xylem,  fills  in  the  spaces  between  the  ducts  consists  chiefly  of 
elongated  parenchymatous  cells  with  thin  walls,  and  a  few  cells 
somewhat  thicker- walled  and  more  fibrous  in  their  character,  but 
hardly  sufficiently  fibrous  to  be  called  wood-cells. 

At  the  outer  and  inner  ends  of  the  bundle  are  the  phloem 
masses,  consisting  of  large  and  well-developed  sieve-cells  and 
smaller  companion-cells,  both  of  which  have  already  been  studied 
(see  Exercise  XIII.).  No  proper  bast-fibres  occur  in  the  bundle. 

Between  the  exterior  phloem  mass  and  the  xylem  is  a  band  of 
meristem-tissue,  several  layers  of  cells  thick,  and  between  the 
inner  end  of  the  xylem  and  the  inner  phloem  mass  is  a  somewhat 
thinner  layer  of  the  same  tissue.  Such  a  bundle,  therefore,  in- 
creases in  length  in  a  radial  direction  by  the  formation  of  new 
cells  in  both  these  layers,  some  of  the  cells  when  mature  con- 
tributing to  the  thickness  of  the  xylem  tissues,  and  others  to 
that  of  the  phloem  masses. 

It  is  very  instructive  to  compare  sections  of  bundles  in  the 
older  with  those  in  the  younger  portions  of  the  stem.  It  will 
then  be  seen  how  much  the  bundles  have  increased  in  length,  and 
in  what  portions  of  the  bundles  the  greatest  increase  of  cells  has 
taken  pla< «  . 


STUDY    OF    COLLATERAL    BUNDLES. 


461 


PLATE  LXXL— Closed  Collateral  Bundle  in  the  Stem  of  Tradescantia  Virginica  (mag- 

155  diameters):  a,  one  of  the  sieve-cells;  b,  one  of  the  sheath-cells;  c,  one  of  the 

starch-bearing  parenchyma-cells  exterior  to  the  bundle;  d,  d,  d,  scalariform  ducts  in 
the  xylem  area  of  the  bundle  ;  e,  a  large  schizogenous  intercellular  space  at  the  older 
portion  of  the  xylem  end  of  the  bundle. 


STUDY    OF   COLLATERAL    BUNDLES. 


463 


k 


PLATE  LXXIL— An  Open  Collateral  Bundle  from  the  above-ground  Stem  of  Saururus 
cernuus  (magnified  210  diameters) :  a,  a,  parenchyma-cells  of  the  fundamental  tissues 
exterior  to  the  bundle;  6,  b,  intercellular  spaces,  c,  c,  c,  large  ducts  in  the  younger 
portions  of  the  xylem ;  d,  bast-fibres ;  e,  soft  bast-tissues ;  /,  meristem  layer ;  g,  spiral 
duct  in  older  part  of  xylem  ;  h,  wood-cell. 


STUDY    OF   COLLATERAL   BUNDLES. 


465 


e 


PLATE  LXXIII.— Bi-collateral  Bundle  from  Stem  of  Cucurbita  Pepo  (magnified  about 

50  diameters) :  a,  a,  parenchyma-cells  exterior  to  bundle ;  b,  b,  large  reticulate  and  pitted 

ducts  in  xylem  ;  c,  c,  sieve-cells  in  outer  and  inner  phloem  respectively ;  d,  d,  outer  and 

inner  meristem  layers  respectively  ;  e,  small  spiral  or  annular  duct  in  older  part  of  xylem. 

30 


EXERCISE  XXIII. 

STUDY  OF    RADIAL  BUNDLES. 

RADIAL  bundles  are  characteristic  of  the  roots  of  all  phaner- 
ogams and  pteridophytes ;  they  occur  also  in  the  stems  of  the 
Lycopodiacese.  As  has  already  been  stated,  their  peculiarity  con- 
sists in  the  fact  that  the  xylem  masses  are  arranged  in  a  radiate 
manner  with  phloem  masses  between  the  rays ;  but  they  present 
a  very  considerable  variety  of  forms,  differing  from  each  other 
not  only  in  the  number  of  rays,  but  in  their  length,  in  the  degree 
of  lignification,  and  in  the  structure  of  the  pericambium-layer 
and  the  endodermis.  There  are  bundles  that  have  as  few  as 
two  xylem-rays,  and  others  that  have  as  many  as  forty  or  fifty. 
The  different  varieties  are  named  according  to  the  number  of  rays 
they  possess,  those  with  two  rays  being  called  diarch,  those  with 
three  rays  triarch,  and  so  on.  The  diarch  bundle  sometimes  so 
closely  approaches  the  concentric  in  structure  that  careful  study  is 
required  to  distinguish  them. 

The  radial  bundles  in  the  roots  of  dicotyls  and  gymnosperms 
usually  differ  from  those  in  the  roots  of  mouocotyls  in  being  fewer- 
rayed  and  in  having  a  thinner-walled  endodermis,  though  the  rule 
has  its  exceptions. 

The  roots  of  the  following  plants  afford  convenient  studies :  the 
Creeping  Crowfoot  (Ranunculus  repens,  L.\  the  Mayapple  (Podo- 
phyllum  peltatum,  L.\  the  Black  Cohosh  (Cimicifuga  racemosa, 
Nutt.),  the  Culver's  Root  (Veronica  Yirginica,  Zr.),  the  Amaryllis 
(Amaryllis  formosissima,  Willd.),  the  Onion  (Allium  Cepa,  L.\ 
the  Sweet  Flag  (Acorns  Calamus,  _L).  the  Indian  Turnip  (Ari- 
ssema  triphyllum,  Torr.\  the  Skunk  Cabbage  (Symplocarpus  fosti- 
dus.  Salisb.\  the  Showy  Lady's  Slipper  (Cypripedium  spectabile, 
Salisb.),  the  Yellow  Lady's  Slipper  (Cypripedium  pubescens, 
Wittd.),  the  Maize  (Zea  Mays,  L.),  the  Sarsaparilla  (Smilax 
officinalis,  KuntK).  and  the  Moonwort  Fern  (Botrychium  Vir- 
ginianum,  Swartz). 

467 


468  LABORATORY    EXERCISES    IN    BOTANY. 

I. — For  the  first  part  of  this  study  let  sections  be  made  of  the 
root  of  Podophyllum  peltatum. 

In  sectioning,  the  roots  should  be  held  between  pieces  of  pith, 
according  to  the  directions  given  for  sectioning  thin  objects  in  the 
Introduction  to  Part  II.  Excellent  sections,  both  longitudinal 
and  transverse,  may  be  produced  by  this  method.  The  sections 
are  best  handled  by  means  of  a  moistened  camel's-hair  brush. 

One  set  of  sections  would  best  be  treated  with  the  anilin-chlo- 
ride  reagent  to  differentiate  the  lignified  xylem-elemeuts ;  but  in 
order  that  all  the  cells  of  the  bundle  may  be  seen  distinctly 
another  set  should  be  treated  with  chloral-hydrate  solution  and 
be  heated  so  as  to  clear  the  tissue  of  starch  ;  or  permanent  prep- 
arations of  great  beauty  may  be  made  by  bleaching  the  sections 
with  Labarraque's  solution,  washing  them  thoroughly,  and  stain- 
ing first  with  iodine-green  and  then,  after  thorough  washing,  with 
ammonia  carmine.  The  sections  are  then,  after  gradual  anhy- 
d ration  by  the  alcohol  process  and  clearing  with  oil  of  cloves, 
mounted  in  xylol  balsam. 

The  bundle  will  usually  be  found  to  be  pentarch,  but  sometimes 
it  is  hexarch  ;  more  rarely  it  has  fewer  than  five  rays,  being  at 
times  even  triarch.  The  xylem-rays  have  at  their  exterior  ter- 
minations very  narrow  reticulate  ducts,  while  in  the  later-formed 
portions  of  the  rays  farther  interior  the  ducts  are  larger  and  are 
mostly  scalariform.  The  central  portion  of  the  bundle  may  or 
may  not  contain  a  few  scattered  ducts,  but  the  greater  portion  is 
composed  of  elongated  parenchymatous  cells. 

The  phloem-tissues,  which,  as  usual,  consist  chiefly  of  sieve- 
and  companion-cells,  are  located  between  the  xylem-rays,  well 
toward  the  outer  extremities  of  the  latter,  and  are  separated 
from  them  by  two  or  three  layers  of  thin-walled  parenchyma- 
cells  on  either  side.  In  sections  which  have  been  cleared  \\ith 
any  of  the  usual  clearing  agents,  as  potassium -hydrate  or  chloral- 
hydrate  solution,  the  sieve-  and  companion-cells  may  readily  be 
distinguished  from  the  other  tissues  by  their  glistening  walls. 

Immediately  interior  to  the  endodermis  is  a  zone  consisting  of 
two  layers  of  thin-walled  cells  of  rather  larger  calibre  than 
either  the  phloem-cells  or  the  endodermal  cells,  and  containing 
small  quantities  of  fine-grained  starch.  This  zone  is  the  peri- 
eaml mini-layer  or  phloem-sheath.  Its  cells  retain  the  power  of 


STUDY    OF    RADIAL    BUNDLES. 


469 


fission,  and  it  is  in  this  layer,  opposite  the  end  of  a  xylera-ray, 
that  a  root-branch  has  its  origin. 

As  in  the  concentric  bundle,  the  radial  bundle  is  enclosed  by 
a  well-developed  endodermis  which  always  consists  of  a  single 
layer  of  cells,  and  which  in  this  as  in  most  other  roots  is  composed 
of  taugentially  elongated  cells.  In  this  case,  as  usually  in  dicotyls, 
the  cells  composing  the  endodermis  remain  thin-walled  and  are  but 
slightly  if  at  all  cutinized. 

II. — Let  a  series  of  transverse  and  longitudinal  sections  of  a 
root  of  Cypripedium  spectabile  be  cut  and  subjected  to  the  same 
treatment. 

In  this  case  the  bundle  will  usually  be  found  to  be  octarch. 
The  xylem-rays  when  the  bundle  is  mature  extend  nearly  or 
quite  to  the  centre,  about  which  are  rather  numerous  reticulate 
ducts  of  large  size,  together  with  thick-walled  xylem-elemeuts  of 
narrower  calibre.  The  outer  portions  of  each  ray,  which  are  com- 
posed of  narrow  reticulate  and  spiral  tracheids,  are  bordered  by 
thick-walled,  lignified  cells  instead  of  the  usual  thin-walled  par- 
enchyma-cells, and  these  thick-walled  cells  extend  clear  to  the 
eudodermis,  so  that  the  pericambium  is  interrupted  in  places. 
The  latter  nowhere  forms  more  than  a  single  layer  of  cells,  and 
seldom  an  interrupted  chain  of  more  than  five  cells.  There  are 
usually  about  this  number  of  pericambium-cells  opposite  each 
phloem  mass,  and  from  one  to  three  at  the  end  of  each  xylem- 
ray. 

Another  peculiarity  is  seen  in  the  structure  of  the  endodermis. 
Opposite  the  lignified  cells  of  the  xylem-rays  and  their  border  of 
thick-walled  cells  the  endodermis  is  composed  of  tangentially 
elongated  but  very  thin-walled  cells,  while  opposite  the  outer 
extremity  of  each  phloem  mass  the  endodermal  cells  have  their 
walls  much  thickened,  but  by  no  means  equally  so.  The  outer 
wall  is  quite  thin,  while  the  radial  walls  are  somewhat  thickened 
and  the  inner  ones  are  excessively  so.  In  consequence  of  this  the 
thickened  portions  look  like  a  crescent  with  the  horns  turned 
outward. 


STUDY   OF    RADIAL   BUNDLES. 


471 


PLATE  LXXIV.— Radial  Bundle  from  the  root  of  Podophyllum  peltatum  (magnified  175 
diameters) :  a,  endodermis ;  b,  pericambium  ;  c,  end  of  one  of  the  xylem-rays ;  d,  phloem 
mass ;  p,  p,  p,  p,  parenchyma-cells  of  the  fundamental  tissues  exterior  to  the  bundle. 


STUDY   OF   RADIAL    BUNDLES. 


473 


a 


PLATE  LXXV.— Radial  Bundle  of  Root  of  Cypripedium  spectabile  (magnified  115 
diameters) :  a,  parenchyma-cell  exterior  to  bundle ;  6,  endodermal  cell  opposite  end  of  a 
xylem-ray:  it  is  tangentially  elongated  and  thin  Availed  ;  c,  a  thick-walled  endodermal 
cell  opposite  the  end  of  a  phloem  mass  ;  d,  large  reticulate  duct  near  centre  of  bundle; 
e,  phloem  mass ;  /,  lignified  cells  bordering  xylem-ray. 


STUDY    OF    RADIAL   BUNDLES. 


475 


PLATE  LXXVL— Small  portion  of  one  of  the  Radial  Bundles  of  Cypripedium  root 
(magnified  500  diameters) :  a,  a  sieve-cell  of  the  phloem ;  6,  one  of  the  ducts  in  a  xylem- 
ray;  c,  c,  thin-walled  endodermal  cells  opposite  the  ends  of  xylem-rays ;  d,  a  thick- 
walled  endodermal  cell  opposite  phloem  mass ;  e,  e,  pericambium-cells ;  /,  parenchyma- 
cell  exterior  to  bundle. 


EXERCISE  XXIV. 

STUDY  OF  EOOTS. 

Two  different  types  of  root  structure  exist  in  the  higher  plants 
—that  observed  in  monocotyls,  and  that  observed  in  dicotyls  and 
in  gymnosperms.  These  two  types  differ  from  each  other  less  in 
their  original  structure  than  in  their  after-development  or  in  the 
secondary  changes  which  they  undergo.  In  general,  it  may  be 
said  that  the  roots  of  monocotyls  possess  a  central  radial  bundle, 
usually  many-rayed  and  enclosed  by  a  thick-walled  endodermis, 
which  bundle  undergoes  few  secondary  changes,  while  the  roots 
of  dicotyls  and  gymuosperms  possess  a  central  radial  bundle, 
usually  few-rayed  and  enclosed  by  a  thin-walled  endodermis, 
which  bundle  undergoes  profound  secondary  changes. 

Monocotyl  roots  favorable  for  study  may  be  observed  in  the 
following  plants :  the  Amaryllis  (Amaryllis  formosissima,  Willd.), 
the  Sarsaparilla  (Smilax  officinalis,  Kunth),  the  Pothos  (Pothos 
pertusa,  Roxb.),  the  Indian  Turnip  (Aristema  triphyllum,  Torr.), 
the  Blue  Flag  (Iris  versicolor,  L.\  the  Sweet  Flag  (Acorus  Cal- 
amus, L.\  the  Yellow  Lady's  Slipper  (Cypripedium  pubescens, 
WiUd.)9  the  Showy  Lady's  Slipper  (Cypripedium  spectabile, 
Salisb.),  the  Reed  Bent  Grass  (Calamagrostis  longifolia,  Hook.), 
and  the  Maize  (Zea  Mays,  L.). 

The  roots  of  the  following  dicotyls  afford  good  studies :  the 
Buttercup  (Ranunculus  septentrionalis,  Poir.\  the  Beet  (Beta 
vulgaris,  Willd.\  the  Carrot  (Daucus  Carota,  L.\  the  Culver's 
Physic  (Veronica  Virginica,  L.\  the  Monkshood  (Aconitum 
Napellus,  L.\  and  the  Black  Cohosh  (Cimicifuga  racemosa, 
Nutt.). 

From  among  gymnosperms,  the  roots  of  any  species  of  Pine  or 
Fir  may  be  studied. 

I. — In  the  first  part  of  this  study  attention  is  directed  to  the 
way  the  root  grows  in  length  and  the  structure  it  shows  at  its 
apex.  For  the  purpose  of  elucidating  these  points  the  root  of 

477 


478  LABORATORY    EXERCISES    IN    BOTANY. 

Calamagrostis  longifolia  is  selected.  The  young  root-tips  of  this 
grass  are  of  such  a  size  that  sections  of  them  may  be  made  with- 
out much  difficulty  by  placing  one  of  the  root-tips  between  t\\o 
flat  pieces  of  cork  that  will  serve  to  direct  the  razor-blade  length- 
wise of  the  root  through  its  middle.  A  common  bottle-cork  a 
centimetre  in  diameter  and  a  centimetre  and  a  half  long  will  serve 
the  purpose  well.  After  halving  the  root-tip  in  the  manner  di- 
rected the  halves  may  again  be  cut  in  a  similar  way  until  the  sec- 
tions are  sufficiently  thin  for  study.  If  the  section  has  passed 
almost  exactly  through  the  middle  of  the  root,  it  will,  when 
properly  mounted  and  examined  with  the  low  power,  present  an 
appearance  similar  to  that  shown  in  Plate  LXXVII. 

The  structure  is  well  shown  if  the  section  be  treated  with 
chloral-hydrate  iodine.  It  is  also  beautifully  shown  by  staining 
the  section  with  Grenadier's  alum  carmine,  anhydrating  it,  and 
mounting  it  in  balsam. 

There  are  three  regions  into  which  every  root  is  divided. 
These,  in  transverse  view,  present  a  series  of  concentric  zones : 
on  the  exterior  the  epidermal,  next  interior  the  cortical,  and  in 
the  centre  the  central-cylinder  region.  The  first  is  usually  thin, 
composed  at  most  of  but  a  few  layers  of  cells ;  the  second  is  com- 
monly of  considerable  thickness,  composed  chiefly  of  parenchyma- 
tous  tissues ;  and  the  third,  also  usually  rather  thick,  is  the  region 
which  contains  the  central  radial  bundle.  The  bundle  is  in  fact 
coextensive  with  the  central  cylinder.  In  Plate  LXXVII.  these 
regions  are  indicated  at  e}  6,  and  a  respectively.  In  the  young 
root,  of  course  (and  in  the  growing  root  that  portion  next  the 
tip  is  always  young),  the  tissues  in  these  regions  are  still  in  a 
nascent  state,  the  cells  are  still  active,  and  distinct  tissues  have 
not  yet  been  developed.  In  this  condition  names  different  from 
those  applied  to  the  mature  structures  are  given  to  the  respective 
regions :  the  nascent  epidermal  region  is  called  the  derniato</<  n  ; 
the  nascent  cortex,  the  periblem  ;  and  the  nascent  central  cylinder, 
the  plerome. 

The  root  has  at  its  extremity  a  cap  quite  easily  distinguishable 
from  the  rest,  and  indicated  in  Plate  LXXVII.  at  //,  //,  and  /.  All 
these  different  layers,  including  the  cap,  have  their  origin  in  the  re- 
gion about  g  (PI.  LXXVII.),  where  there  is  a  mass  consisting  of 
a  large  number  of  meristem-cells.  It  will  be  noticed  that  the  cells 


STUDY   OF   ROOTS.  479 

on  ail  sides  of  this  area  are  arranged  in  rows  focusing  at  this  grow- 
ing-point. At  i  is  the  younger  portion  of  the  root-cap,  with  its 
cells  still  arranged  as  just  described,  while  at  h  and  hf  are  the 
older  portions  of  the  cap,  composed  of  larger  and  thicker-walled 
cells  in  which  the  radial  arrangement  has  become  obscured.  At 
the  surface  of  the  cap  the  cells  are  even  becoming  disintegrated. 
At/  is  a  transparent  area  consisting  of  the  thickened  and  muci- 
laginous outer  wall  of  the  epidermis.  At  d  is  distinguishable, 
though  not  without  some  difficulty,  the  endodermis,  constituting 
the  inner  layer  of  the  cells  of  the  cortex.  At  this  stage  in  the 
development  of  the  endodermis  it  is  clear  that  it  belongs  to  the 
cortex  rather  than  to  the  central  cylinder.  At  c  is  a  row  of 
cells  already  considerably  larger  than  the  neighboring  ones :  they 
constitute  the  beginnings  of  a  duct.  Higher  up  in  the  root  it 
would  be  found  that  the  cells  composing  the  row  had  lost  their 
protoplasm,  that  their  walls  had  acquired  distinct  markings,  and 
that  the  transverse  partitions  had  wholly  or  partially  disap- 
peared. 

The  student  should  carefully  compare  a  transverse  section  of 
the  older  portion  of  a  root  with  the  longitudinal  section  just  stud- 
ied, trace  the  correspondence  of  parts,  and  also  note  the  changes 
which  have  developed  during  growth. 

In  nearly  all  pha3nogamous  plants  the  structure  and  growth  of 
the  root  at  its  apex  resemble  those  of  Calamagrostis  ;  but  in  some 
of  the  higher  cryptogams  (the  Ferns  and  Equisetse)  the  growing- 
point  or  punctum  vegetationis,  corresponding  to  g  in  the  drawing, 
consists  of  a  single  cell  instead  of  a  cluster  of  cells.  In  these 
plants  all  the  tissues  of  the  root — root-cap,  epidermis,  cortex,  and 
central  cylinder — originate  by  the  successive  cutting  off  of  cells 
from  a  somewhat  triangular  generative  cell  located  at  the  punctum 
vegetationis. 

II. — Let  now  the  secondary  changes  that  usually  take  place  in 
the  central  cylinder  of  the  roots  of  dicotyls  and  gymnosperms  be 
studied  in  the  adventitious  roots  which  spring  from  the  rhizome 
of  Cimicifuga  racemosa. 

In  a  root  twelve  or  fifteen  centimetres  long,  sections  made  a 
centimetre  or  two  back  of  the  apex  will  show  scarcely  any 
change ;  three  centimetres  or  so  back  of  the  apex,  considerable 
changes  will  be  observed ;  and  four  or  five  centimetres  back, 


480  LABORATORY    EXERCISES    IN    BOTANY. 

very  decided  changes.  Let  such  a  series  of  sections  be  prepared 
and  be  treated  with  chloral-hydrate  iodine  solution. 

Focusing  with  a  low  or  moderate  power  on  a  section  from  near 
the  apex  of  the  root,  the  usual  structure  of  a  radial  bundle  will 
be  observed.  Different  roots  of  the  species  will  vary  as  to  the 
inunber  of  rays,  some  being  triarch,  others  tetrarch,  and  still 
others  pentarch,  but  all  agree  in  possessing  a  central  pithy  por- 
tion, short  xylem-rays  with  the  smaller  ducts  pointing  toward  the 
exterior,  rounded  masses  of  phloem  between  the  exterior  ends  of 
the  xylem-rays  and  separated  from  them  by  two  or  three  layers 
of  parenchyma,  and  a  pericambium  consisting  of  about  two  layers 
of  cells.  Separating  the  bundle  from  the  cortex  is  also  a  distinct 
endodermis. 

A  section  made  at  a  point  a  little  higher  up  on  the  root  shows 
that  the  bundle  has  increased  in  size.  The  cells  of  the  endoder- 
mis have  become  more  numerous  by  radial  division  ;  the  ends  of 
the  xylem-rays  are  now  farther  removed  from  the  endodermis, 
proving  that  the  intervening  tissues  have  increased  by  division 
of  the  cells ;  new  ducts  have  formed  on  either  side  of  the  inte- 
rior ends  of  the  xylem-rays,  and  evidences  are  seen,  from  the 
increase  in  size  of  some  of  the  cells,  that  still  others  are  forming 
farther  interior ;  and  a  layer  of  meristem  is  traceable  around  the 
exterior  end  of  each  xylem-ray,  along  its  sides,  and  extending 
across  from  the  base  of  one  ray  to  the  next,  behind  each  phloem 
mass,  and  so  forming  a  complete  but  wavy  girdle — in  fact,  a 
cambium  zone — running  in  and  out  between  phloem  and  xylem. 
Furthermore,  evidences  are  seen,  in  the  increased  quantity  of 
starch  in  the  several  layers  of  cells  immediately  interior  to  the 
endodermis,  that  these  cells  are  passing  over  into  the  condition  of 
permanent  tissues. 

If  now  a  section  from  a  still  older  portion  of  the  root  be  exam- 
ined, more  decided  changes  will  be  seen.  The  endodermis  is  still 
traceable,  but  is  much  farther  removed  from  the  centre  and  en- 
closes a  much  larger  bundle.  The  parenchyma-cells  exterior  to 
the  eudodermis,  by  reason  of  the  pressure  due  to  the  growth  in  the 
area  interior  to  the  endodermis,  have  become  tangential! y  stivtdiod, 
and  so  also  have  the  starch-bearing  cells  interior  to  the  endo- 
dcrmis.  In  the  interior  of  the  bundle,  in  the  specimen  from 
which  the  drawing  was  made  (PL  LXXIX.),  four  broadly  wedge- 


STUDY    OF    ROOTS.  481 

shaped  medullary  rays  separate  laterally  four  broad,  somewhat 
wedge-shaped  xylem  masses  which  meet  at  the  centre  to  form  a 
figure  resembling  a  Maltese  cross.  At  the  outer  extremity  of 
each  xylem  mass  is  a  triangular  mass  of  phloem  with  its  broad 
base  resting  upon  a  layer  of  cambium  which  separates  the  phloem 
from  the  xylem  and  is  continued  across  the  medullary  ray  to  the 
next  arm  of  the  cross,  and  so  around.  The  cambium  zone,  though 
still  somewhat  wavy,  has  become  less  so  than  in  the  last  section. 
At  the  inner  angle  of  the  medullary  rays  are  still  recognizable  the 
four  original  xylem-rays,  and  at  the  outer  ends  of  the  triangular 
masses  of  phloem  are  the  original  phloem  masses  which  in  the 
young  bundle  lay  between  the  ends  of  these  rays.  It  will  be 
seen  that  there  must  have  been  an  enormous  new  growth  of 
cells  in  the  cambium  zone  to  form  the  new  wood  wedges  and 
medullary  rays  and  to  push  so  far  outward  the  phloem  masses 
and  the  boundaries  of  the  bundle. 

The  root  of  Cimicifuga  may  be  taken  as  illustrating  in  a  simple 
way  the  most  important  features  of  the  secondary  changes  which 
occur  in  the  roots  of  the  great  majority  of  dicotyls  and  gymno- 
sperms.  These  changes  sharply  distinguish  the  roots  of  these  two 
groups  of  plants  from  those  of  monocotyls  and  vascular  crypto- 
gams, in  which  no  cambium  zone  is  formed. 

The  root  of  Cimicifuga,  however,  differs  in  some  minor  par- 
ticulars from  the  roots  of  many  other  dicotyls  and  from  those  of 
gymnosperms.  For  example,  the  broad  medullary  rays  above  de- 
scribed are  the  only  ones  recognizable  in  Cimicifuga,  while  in  the 
roots  of  many  other  plants  of  its  sub-class,  and  in  those  of  gym- 
nosperms, the  newly-formed  phloem  and  xylem  masses  are  crossed 
by  secondary  medullary  rays  often  narrower  than  the  primary 
ones,  but  similarly  arranged,  so  that  the  new  formations  are 
divided  into  a  series  of  radially-arranged  bundles  like  the  open 
collateral  ones  in  the  stems  of  the  same  plants.  In  fact,  to  the 
eye,  often  the  most  conspicuous  difference  between  the  mature 
stem  and  the  mature  root  of  a  dicotyl  or  a  gymnospermous  plant 
is  the  presence  of  a  pith  in  the  former  and  its  absence  in  the  latter. 


STUDY    OF    ROOTS. 


483 


PLATE  LXXVIL— Longitudinal  Section  through  the  centre  of  the  Root-tip  of  Calama- 
grostis  longifolia  (magnified  about  100  diameters) :  a,  plerome-cylinder ;  6,  b,  periblem  ; 
e,  e,  dermatogen;  c,  duct  in  process  of  formation;  d,  endodermis  ;  e,  thickened,  mucilag- 
inous outer  wall  of  forming  epidermal  layer ;  g,  punctum  vegetationis ;  h,  h',  older 
portions  of  root-cap ;  i,  younger  portion  of  root-cap  still  showing  radial  arrangement 
of  its  cells. 


STUDY   OF   BOOTS. 


485 


CL 


PLATE  LXXVIIL— Part  of  Transverse  Section  of  younger  portion  of  Root  of  Cimicifnga 
racemosa,  showing  radial  bundle  not  much  changed  by  secondary  formations  (magni- 
fication, 100  diameters) :  a,  starch-bearing  parenchyma-cell  of  the  cortex ;  &,  endodermis  ; 
c,  pericambium ;  d,  small  ducts  at  the  outer  extremity  of  one  of  the  four  xylem-rays ; 
e,  phloem  mass ;  /,  /,  meristem  tissue  beginning  to  form  back  of  the  phloem  mass  and 
between  it  and  the  xylem-rays  on  either  side. 


STUDY   OF    ROOTS. 


487 


PLATE  LXXIX.— Section  from  an  older  portion  of  the  Root  of  Cimicifuga  racemosa, 
showing  the  secondary  changes  much  farther  advanced  (magnification  the  same  as  in 
the  previous  figure):  a,  starch-bearing  parenchyma-cell  of  cortex;  &,  endodermis;  e, 
one  of  the  four  phloem  masses  ;  d,  meristem  formed  back  of  one  of  the  phloem  masses; 
e,  extremity  of  one  of  the  xylem-rays ;  /,  starch-bearing  colls  interior  to  endodermis; 
g  cambium  formed  over  the  end  of  a  xylem-ray,  and  continued  into  a  wavy  girdle 
running  in  and  out  between  the  phloem  and  xylem  masses;  h,  new  ducts  that  have 
been  formed  behind  a  phloem  mass. 


STUDY   OF    ROOTS. 


489 


PLATE  LXXX.— Part  of  section  of  still  older  portion  of  a  Root  of  Cimicifuga  racemosa 
(magnification  about  50  diameters) :  a,  a  starch-bearing  parenchyma-cell  of  the  cortex  ; 
b,  endodermis ;  c,  cambium ;  d,  duct  in  secondary  xylem ;  e,  one  of  the  starch-bearing 
cells  of  the  broad,  wedge-shaped  medullary  ray ;  /,  outer  extremity  of  one  of  the  four 
original  xylem-rays  ;  h,  cambium  of  medullary  ray. 


EXERCISE  XXV. 
DIFFERENT  TYPES  OF   STEMS. 

AMONG  vascular  cryptogams  and  phanerogams  four  different 
types  of  stem  structure  may  be  recognized  :  the  fern  type,  the 
club-moss  type,  the  mouocotyl  type,  and  the  dicotyl  type. 

The  fern  type  may  be  studied  in  the  rhizomes  of  the  following 
ferns  :  Polypodium  vulgare,  L.,  Pteris  aquiliua,  L.,  Aspidium 
Thelypteris,  Swartz,  A.  spiuulosum,  Swartz,  A.  marginale,  Swartz, 
and  A.  Filix-mas,  Swartz. 

The  club-moss  type  may  be  studied  in  the  following  species  of 
Lycopodium :  L.  clavatum,  L.,  L.  Selago,  L.,  L.  inundatum,  L., 
and  L.  obscurum,  L. 

The  monocotyl  type  is  conveniently  studied  in  any  of  the  fol- 
lowing plants  :  the  Greenbrier  (Smilax  rotundifolia,  L.),  the  As- 
paragus (Asparagus  officinalis,  L.\  the  False  Solomon's  Seal 
(Smilacina  racemosa,  Desf.),  the  Solomon's  Seal  (Polygonatum 
biflorum,  Ell),  the  Tiger  Lily  (Lilium  tigrinurn,  Ker),  the  Wild 
Yellow  Lily  (Lilium  Canadense,  L.),  the  White  Hellebore  (Vera- 
trum  viride,  Ait.),  the  Pickerel  Weed  (Pontederia  cordata,  L.),  the 
Spiderwort  (Tradescantia  Virginica,  L.),  the  Indian  Turnip  (Ari- 
ssema  triphyllum,  Torr.),  the  Indian  Corn  (Zea  Mays,  L.),  and  the 
Wheat  (Triticum  vulgare,  Villars). 

The  dicotyl  type  is  well  illustrated  in  the  stems  of  any  of  the 
following :  the  Black  Cohosh  (Cimicifuga  racemosa,  Nutt.),  the 
Cocculus  (Cocculus  Carolinus,  DC.),  the  Yellow  Parilla  (Menis- 
permtira  Canadeuse,  L.),  the  Virgin's  Bower  (Clematis  Virgin iana, 
L.),  the  Basswood  (Tilia  Americana,  L.),  the  Silver  Maple  (Acer 
dasycarpum,  Ehrh.\  the  Licorice  (rhizome)  (Glycyrrhiza  glabra, 
L.),  the  Witch  Hazel  (Harnamelis  Virginiana,  L.),  the  Parsnip 
(Pastinaca  sativa,  L.),  the  Pumpkin  (Curcurbita  Pepo,  L.\  the 
Pipe  Vine  (Aristolochia  Sipho,  77 Tier.),  the  Sycamore  (Platan us 
occidentalis,  L.\  the  Lizard's  Tail  (Saururus  cernuus,  L.\  and, 
among  gymnosperms,  the  White  Pine  (Pinus  Strobus,  Z.),  the 

491 


492  LABORATORY    EXERCISES    IN    BOTANY. 

Tamarack  (Larix  Americana,  Michx.),  and  the  Bald  Cypress 
(Taxodium  distichum,  Richard.). 

I.  THE  FERN  TYPE. — Let  cross-sections  be  made  of  the  rhi- 
zome of  Pteris  aquilina,  and,  that  the  vasal  bundles  may  well  ho 
seen,  let  one  of  the  sections  be  treated  with  the  phloroglucin  re- 
agent. The  appearance  presented  under  a  very  low  magnifying 
power  is  that  shown  in  Figure  1  (PL  LXXXL).  At  the  outside? 
is  the  epidermis,  composed  of  a  layer  of  thick- walled  cells  who.-c 
walls  are  colored  deep-brown,  and  immediately  interior  to  it  are 
several  tiers  of  thick-walled  cells,  also  colored  brown,  consti- 
tuting the  hypoderma.  Together  these  constitute  the  darkly 
shaded  area  indicated  at  a,  a  in  the  drawing.  A  hypoderma 
is  very  commonly,  though  not  always,  developed  in  the  stems 
of  ferns. 

Interior  to  the  hypoderma  is  a  rather  thick  portion  of  cortex 
consisting  almost  wholly  of  thin-walled  parenchyma-cells  con- 
taining starch.  It  may,  however,  contain  a  few  small  clusters  of 
dark-colored  sclerenchyma-fibres  as  indicated  at  6.  There  is  in 
this  case  no  sharp  line  of  demarkation  between  the  central  cylin- 
der and  the  cortex.  The  central  cylinder,  however,  is  the  area 
which  includes  the  vasal  bundles,  no  bundles  being  found  in  the 
cortex  save  where  a  branch  passes  off  from  one  or  more  of  the 
bundles  to  supply  a  root  or  a  leaf.  If  an  imaginary  line  be 
drawn  around  the  exterior  bundles,  which  form  a  circle,  in  such 
a  manner  as  to  touch  the  outside  of  each  of  them,  this  line  would 
form  the  boundary  between  the  cortex  and  the  central  cylinder. 
There  are  thus  the  same  three  regions  in  the  stem  as  in  the  root : 
the  epidermal  region,  the  cortical  region,  and  the  central-cylinder 
region. 

Most  of  the  vasal  bundles  are  elongated,  those  forming  the  cir- 
cle being  elongated  in  a  tangential  direction,  and  the  two  large 
bundles  near  the  centre  being  elongated  in  the  direction  of  the 
longer  diameter  of  the  somewhat  flattened  stem. 

Interior  to  the  circle  of  bundles  and  exterior  to  the  largo  cen- 
tral bundles  are  two  long,  somewhat  curved  masses  of  dark-colored 
sclerenohy  ma-fibres,  the  larger  one  of  the  two  being  indicated  at 
c  in  the  drawing. 

The  vasil  bundles,  as  has  already  been  learned  (Exercise  XX  I .), 
an-  <>!'  the  concentric  type,  and  of  that  form  of  it  in  which  the 


DIFFERENT   TYPES    OF    STEMS.  493 

xylem  is  located  centrally.  If  longitudinal  sections  of  the  stem 
were  to  be  studied,  it  would  be  found  that  the  bundles  in  the 
circle  do  not  remain  wholly  independent  of  each  other  through- 
out their  course,  but  that  they  occasionally  anastomose,  and 
besides  this  send  off  branches  to  supply  the  leaves. 

There  are  some  features  in  the  structure  of  the  stein  of  Pteris 
aquilina  which  are  not  found  in  all  fern  stems,  and  which  are 
therefore  not  essential  to  the  type. 

What,  then,  are  the  essential  features  of  the  type  ?  They  con- 
sist (1)  in  the  kind  and  (2)  in  the  arrangement  of  the  bundles. 
The  bundles  are,  with  few  exceptions,  of  the  concentric  type, 
with  the  xylem  in  the  centre,  and  they  are  arranged  in  one  or 
more  circles,  with  frequently  a  tangential,  but  never  a  radial, 
elongation.  There  may  or  may  not  be  extra  bundles  and  masses 
of  sclerenchy ma-fibres  enclosed  by  the  primary  circle  of  bundles. 

Such  stems  possess  no  cambium  zone,  and  increase  in  thickness 
is  therefore  limited.  A  fern  stem  forty  years  old  is  no  larger  near 
its  base  than  near  its  apex. 

II.  THE  CLUB-MOSS  TYPE. — Let  cross-sections  now  be  made 
of  the  common  Club  Moss,  Lycopodium  obscurum,  and  let  one 
of  them  be  treated  with  the  phloroglucin  reagent  and  another 
with  chloral-hydrate  iodine.  The  former  will  enable  one  to  dis- 
tinguish more  clearly  the  xylem  elements  of  the  central  cylinder, 
and  the  latter  will  better  define  the  phloem  elements. 

Under  a  low  magnifying  power  the  section  will  appear  as  shown 
in  Figure  2  (PL  LXXXL).  a  is  the  epidermis,  consisting  of 
a  single  layer  of  thickish-walled,  cutinized,  and  often  somewhat 
lignified  cells ;  b  is  an  area  of  thin-walled  cells  belonging  to  the 
exterior  cortex,  but  the  larger  portion  of  the  cortex  is  composed 
of  excessively  thick-walled  cells  or  fibres  (sclereuchyma-fibres). 
The  central  cylinder  is  here  sharply  marked  off  from  the  cortex 
by  an  area  of  thin-walled  tissues,  the  outer  of  which  layer  of 
tissues  probably  represents  an  endodermis,  though  it  is  not  very 
different  in  appearance  from  the  rest  of  the  tissues  in  this  area. 
In  the  centre  is  another  area  composed  of  plates  of  xylem  with 
scalariform  tracheids  separated  from  each  other  by  plates  of 
phloem. 

The  bundle  would  best  be  regarded,  perhaps,  as  a  radial  bundle 
— in  this  particular  case  a  fourteen-rayed  one  ;  but  it  might  be  re- 


494  LABORATORY    EXERCISES    IN    BOTANY. 

garded  differently  :  each  plate  of  xylem  with  the  adjacent  plates 
of  phloem  might  be  looked  upon  as  constituting  an  incomplete 
concentric  bundle  like  that  in  ferns.  Thus  the  central  cylinder 
would  be  composed  of  a  group  of  imperfectly-formed  concentric 
bundles  enclosed  by  a  common  endodermis.  In  the  sterns  of  the 
Selaginellse,  related  to  the  Lycopodii,  there  are  usually  two  or 
more  separate  concentric  bundles  arranged  side  by  side.  The 
relationship  is  thus  seen  between  the  concentric  and  the  radial 
bundle. 

The  club-moss  type  of  stem,  then,  is  one  in  which  the  central 
cylinder  is  occupied  either  by  a  single  radial  bundle  or  by  two  or 
more  concentric  bundles  arranged  side  by  side. 

III.  THE  MONOCOTYL  TYPE. — For  the  study  of  the  mono- 
cotyl  type  of  stem  let  transverse  sections  be  made  of  the  stem  of  the 
common  Maize.  A  section  stained  by  means  of  the  anilin-chlo- 
ride  reagent  will  serve  the  purpose  well.  Under  a  very  low  mag- 
nifying power  the  stem  presents  the  appearance  shown  in  Figure  1 
(PL  LXXXII.).  On  one  side  of  the  stem  is  a  notch,  a,  into  which 
fitted  the  axillary  bud  borne  on  the  node  below.  At  the  exterior 
of  the  section  is  the  epidermis,  composed,  as  usual,  of  a  single 
stratum  of  cells.  Interior  to  this  is  the  cortex,  composed,  in  the 
present  instance,  of  only  a  few  layers  of  thin-walled  cells,  and 
not  separated  from  the  central  cylinder  by  a  sheath,  as  is  some- 
times the  case  in  this  type  of  stem.  The  central  cylinder  is  com- 
posed of  parenchymatous  ground  tissues  through  which  very 
numerous  bundles  are  scattered.  These  bundles  are  smaller  and 
closer  together  next  the  outside,  where  sometimes  two  or  more 
partially  coalesce.  The  bundles  are  all  of  the  closed,  collateral 
type,  and,  as  is  usual  in  this  kind  of  stem,  the  phloem  faces  exte- 
riorly and  the  xylem  faces  toward  the  centre  of  the  stem.  The 
xylem  portion  of  each  bundle  usually  contains  about  two  large 
ducts  toward  its  outer  face,  next  the  phloem,  and  several  smaller 
ones  toward  its  inner  face,  where  also  there  is  usually  to  be  found 
an  irregular  intercellular  space  of  considerable  size.  Tin;  bundle 
is  ensheathed  by  thick- walled  fibres,  most  abundant  and  thieke-t 
walled  at  the  outer  and  inner  ends  of  the  bundle.  Those  fibres 
at  the  outer  or  phloem  end  may  be  called  bast-fibres ;  those  at  the 
inner  or  \ylem  end,  wood-cells. 

The  closed  collateral  bundle  is  commonest  in  the  stems  of  mono- 


DIFFERENT    TYPES    OF    STEMS.  495 

cotyls,  though,  as  has  been  seen,  the  concentric  bundle  with  a  cen- 
tral phloem  sometimes  occurs. 

The  arrangement  of  bundles  is  also  usually  similar  to  that  in 
Maize,  but  sometimes  there  are  deviations  more  or  less  conspicuous. 
In  most  of  the  other  grasses,  for  example,  bundles  are  wanting  at 
the  centre  of  the  stem,  and  the  latter  at  maturity  becomes  hollow  by 
the  rupture  of  the  parenchymatous  cells.  In  the  stems  of  Dracaenas 
and  in  some  other  woody  Liliacese  there  is  a  kind  of  cambium  area 
in  the  boundary  region  between  the  central  cylinder  and  the  cor- 
tex in  which  new  parenchyma  and  new  bundles  are  formed,  so 
that  such  stems  increase  in  diameter  from  year  to  year  as  do  those 
of  dicotyls.  But  the  bundles  themselves  in  kind  and  arrangement 
are  similar  to  those  in  the  stems  of  other  monocotyls.  (See  College 
Botany,  pp.  187,  188.)  In  a  few  monocotyls  also,  as  in  the  Yams, 
the  stem  structure  closely  approaches  that  of  dicotyls. 

To  understand  the  distribution  of  the  bundles  in  the  monocotyl 
stem  their  course  lengthwise  of  the  stem  must  be  traced.  It  must 
be  understood  that  the  bundles  of  the  stem  are  continuous  with 
those  in  the  leaves,  and  that  if  the  course  of  the  bundles  be  traced 
from  the  leaves  into  the  stem,  it  will  be  found  that  some  of  the 
bundles,  after  passing  through  the  cortex  into  the  central  cylinder, 
turn  immediately  downward,  while  others  do  not  bend  downward 
until  they  have  passed  farther  toward  the  centre  of  the  stem.  It 
thus  happens  that  the  downward  course  of  some  bundles  is  near 
the  outside  of  the  central  cylinder,  of  others  a  little  farther  inte- 
rior, and  of  still  others  near  the  centre.  The  distribution  of  the 
bundles  already  seen  in  cross-section  is  thus  easily  accounted  for. 

The  downward  course  of  the  bundles  is,  however,  not  usually 
quite  parallel  to  the  surface  of  the  stem,  but  the  bundles  incline 
a  little  outward  until  they  finally  terminate  either  in  the  roots 
or  in  the  surface  of  the  central  cylinder.  During  this  down- 
ward course  they  become  smaller  in  size  by  the  loss  of  some  of 
their  elements,  until  at  their  termination  they  may  be  quite  de- 
pauperate. These  facts  account  for  the  smaller  size  and  the  more 
crowded  condition  of  the  bundles  toward  the  periphery  of  the 
central  cylinder. 

IV.  THE  DICOTYL  TYPE. — The  stem  of  Meuispermum  Cana- 
deuse  is  taken  to  illustrate  one  of  the  simplest  forms  of  the  dicotyl 
type  of  stem  structure.  Cross-sections  should  be  made  both  from 


496  LABORATORY    EXERCISES    IN    BOTANY. 

old  and  from  young  portions  of  the  stem — a  series,  for  example, 
from  a  stem  less  than  a  year  old,  another  from  one  about  two 
years  old,  and  a  third  from  a  still  older  stem.  One  set  of  sec- 
tions may  be  treated  with  the  anilin-chloride  reagent,  and  another 
with  the  chloral-hydrate  iodine  solution. 

Let  sections  of  the  youngest  portion  of  the  stem  first  be  exam- 
ined. Here  three  regions  are  distinguished  :  the  epidermal,  the 
cortical,  and  the  central-cylinder  region. 

Beneath  the  one-layered  epidermis,  which  in  this  plant  persists 
for  a  long  time  and  ultimately  forms  a  very  thick  cuticle  at  its 
surface,  is  the  thickish  cortex,  composed  almost  wholly  of  paren- 
chyma, constituting  the  middle  or  green  layer  of  the  bark  (rneso- 
pbloeom).  In  the  central  cylinder  lie  the  open  collateral  bundles, 
arranged  radially  about  a  central  parenchyma — the  pith  or  me- 
dulla— like  the  spokes  of  a  wheel  about  its  hub.  Each  bundle  is 
separated  laterally  from  the  next  by  a  plate  of  thin-walled  paren- 
chyma constituting  a  medullary  ray.  The  xylern  of  each  bundle 
faces  the  pith,  the  phloem  faces  the  cortex,  and  the  xylem  is  com- 
posed chiefly  of  large  ducts  and  much  smaller  wood-cells,  while 
the  phloem  forms  a  smaller  mass  and  is  made  up  chiefly  of  sieve- 
aud  companion-cells  on  its  inner  side  and  of  a  crescent-shaped 
mass  of  bast-fibres  on  its  outer  side. 

Between  phloem  and  xylem  is  meristem,  which  has  the  usual 
characteristics  of  this  tissue.  Because  it  is  a  part  of  the  bundle 
it  is  called  the  "  fascicular  cambium."  The  meristem  is,  however, 
continued  across  the  medullary  ray  from  one  bundle  to  the  next, 
and  thus  forms  a  zone  that  separates  the  central  cylinder  into  two 
portions :  an  inner  portion,  which  includes  the  xylem  part  of  all 
the  bundles,  the  pith,  and  the  inner  portion  of  the  medullary  rays, 
and  which  is  often  called  the  woody  cylinder;  and  an  outer  por- 
tion, which  includes  the  phloem  masses  and  the  intervening  outer 
ends  of  the  medullary  rays,  and  which  together  constitute  the  inner 
or  bast  layer  of  the  bark  (eudophloeum). 

Examining  now  one  of  the  next  older  series  of  sections,  it  is 
found  that  the  stem  has  considerably  increased  in  diameter  and 
that  the  bundles  are  measurably  longer  in  a  radial  direction. 
Moreover,  the  xylem  part  of  the  bundles  has  increased  in  length 
proportionally  much  more  rapidly  than  the  phloem  portions.  The 
cells  of  the  phloem  may,  however,  easily  be  ascertained  to  have 


DIFFERENT  TYPES  OF  STEMS.  497 

increased  considerably  in  number.  The  older  sieve-tissues  have, 
in  fact,  by  the  formation  of  others  interior  to  them,  been  crowded 
up  together  against  the  unyielding  bast-fibres  until  the  cells  appear 
collapsed. 

If  the  section  is  from  a  stem  two  years  old,  two  evident  rings 
(rings  of  growth)  will  be  seen  in  the  wood ;  if  the  stem  is  three 
years  old,  three  rings  will  be  seen,  and  so  on.  In  a  stem  three 
years  old  or  more,  bundles  may  often  be  seen  which  are  divided 
into  two  at  their  outer  extremity,  each  branch  of  the  bundle  being 
separated  from  the  other  by  a  short  medullary  ray.  Such  old 
stems  may  have  the  epidermis  ruptured  in  places  by  the  formation 
of  cork -cells  underneath. 

In  some  respects  the  stem  of  Menispermum  differs  from  the 
stems  of  most  other  dicotyls,  but  in  nearly  all  dicotyls  and  gym- 
nosperms  the  bundles  are  of  the  open  collateral  type,  arranged 
radially  about  a  central  pith  and  separated  laterally  from  each 
other  by  medullary  rays. 

Most  woody  dicotyls  differ  from  Meuispermum  in  having  nar- 
row, lignified  medullary  rays  which  are  also  much  shorter  both  in 
a  radial  and  in  a  longitudinal  direction.  The  first-formed  bun- 
dles, usually  few  in  number,  divide  repeatedly  at  the  outer  ex- 
tremities, so  that  the  medullary  rays  become  increasingly  numer- 
ous as  the  stem  grows  older. 

The  course  of  the  bundles  in  a  dicotyl  stem  is  well  shown  on 
p.  189  of  College  Botany  (Figure  450),  to  which  the  student  is 
referred. 

In  gymnosperms  the  arrangement  of  the  bundles  is  similar  to 
that  in  dicotyls,  though  the  stems  of  the  one  may  readily  be  dis- 
tinguished from  those  of  the  other  by  the  structure  of  their  woody 
tissues,  as  explained  in  Exercise  XI. 

So  far  as  the  apex  of  the  stem  is  concerned,  in  structure  and  in 
mode  of  growth  it  differs  little  from  the  root  save  in  the  absence 
of  a  cap.  The  growing-point  is  at  the  apex  instead  of  just  back 
of  it,  and  in  the  club-mosses  and  phanerogams  the  growth  takes 
place  from  a  cluster  of  cells,  while  in  the  Equisetse  and  ferns  it 
takes  place  from  a  single  cell,  as  in  the  roots  of  the  same  plants. 

32 


DIFFERENT   TYPES   OF   STEMS. 


a 


PLATE  LXXXL,  FIG.  1.— Transverse  Section  of  Rhizome  of  Pteris  aquilina  (magnified 
about  7  diameters) :  a,  a,  hypoderma  ;  b,  small  cluster  of  sclerenchyma-fibres  in  cortex ; 
c,  one  of  the  circle  of  concentric  bundles;  d,  one  of  the  two  interior  large  bundles; 
e,  one  of  the  two  large  brown  masses  of  sclerenchyma-fibres. 

FIG.  2.— Transverse  Section  of  Stem  of  Lycopodium  obscurum  (magnified  30  diameters): 
o,  epidermis ;  6,  thin-walled  cells  of  cortex  beneath  epidermis ;  c,  sclerenchyma-fibres 
constituting  the  principal  portion  of  the  cortex ;  rf.  soft  tissue  (pericambium)  in  outer 
portion  of  central  radial  bundle;  e,  one  of  the  xylem-rays;  /,  a  leaf-base;  g,  vasal 
bundle  in  another  leaf-base  ;  h,  a  vasal  bundle  passing  off  to  supply  a  leaf. 


DIFFEKENT   TYPES   OF   STEMS. 


501 


a 


PLATE  LXXXIL,  FIG.  1.— Transverse  Section  of  Stem  of  Maize  (magnified  about  4 
diameters) :  a,  epidermis ;  b,  thin  cortex ;  c,  indentation  caused  by  a  bud  formed  on 
internode  below ;  d,  one  of  the  small  bundles  among  the  crowded  ones  at  the  outside  of 
the  central  cylinder. 

FIG.  2.— Transverse  Section  of  Stem  of  Menispermum  Canadeuse  in  the  third  year  of  its 
growth  (magnified  8  diameters) :  a,  cortex ;  6,  crescent-shaped  mass  of  bast-fibres ;  c, 
medullary  ray  ;  d,  xylem  of  a  bundle ;  e,  pith ;  /,  soft  tissues  of  phloem ;  g,  fascicular 
cambium  ;  h,  interfascicular  cambium. 


EXERCISE  XXVI. 

STUDY  OF  LEAF  STKUCTUKE. 

LEAVES,  so  far  as  their  internal  structure  is  concerned,  are  of 
two  principal  types,  the  bifacial  and  the  centric.  These  types 
differ  chiefly  in  the  arrangement  of  the  chlorophyll-bearing 
parenchyma.  In  the  bifacial  type  the  parenchyma  consists  of 
two  quite  different  layers  facing  the  upper  and  lower  surfaces  re- 
spectively. The  layer  facing  the  upper  surface  has  its  cells  com- 
pactly arranged  and  usually  elongated  in  a  direction  perpendicular 
to  the  epidermis,  forming  what  is  called  palisade  parenchyma  ; 
the  layer  facing  the  lower  surface  has  its  cells  loosely  arranged 
and  usually  little  if  at  all  lengthened  perpendicularly  to  the  epi- 
dermis. In  leaves  of  this  kind  the  blade  is  always  flattened,  and 
habitually  presents  the  deeper  green  surface,  next  which  lies  the 
palisade  layer,  upward  or  toward  the  stronger  light.  This  surface 
usually  has  few  or  no  stomata,  while  on  the  other  surface  they  are 
numerous. 

In  the  centric  type  of  leaf  there  is  but  little  structural  dif- 
ference between  the  parenchyma-layers  facing  the  two  surfaces, 
and  seldom  is  anything  resembling  a  palisade  tissue  developed 
next  either  surface,  although,  as  a  rule,  the  parenchyma  is  more 
spongy  in  the  interior,  is  larger-celled,  and  contains  less  chloro- 
phyll than  the  parenchyma  adjacent  to  the  surfaces.  Terete,  acic- 
ular,  and  succulent  leaves  usually  belong  to  this  class,  but  it  may 
include  flattened  and  even  membranous  forms.  In  this  case,  how- 
ever, the  two  surfaces  are  nearly  equally  exposed  to  the  light,  and 
both  possess  stomata. 

The  following  plants  afford  a  good  variety  for  study  :  Bifacial 
leaves:  the  Male  Fern  (Aspidium  Filix-mas,  Swartz),  the  Sago 
Palm  (Cycas  revoluta,  Willd.),  the  Begonia  (Begonia  discolor, 
H.  jfif.),  the  Eucalyptus  (Eucalyptus  globulus,  Lab.\  the  Rue 
(Ruta  graveolens,  Willd.},  the  Oleander  (Nerium  Oleander,  L.\ 

503 


504  LABORATORY    EXERCISES    IN    BOTANY. 

the  Rubber  Tree  (Ficus  elastica,  Roxb.),  the  Nettle  (Urtica  dioica, 
L),  the  Beech  (Fagus  ferruginea,  Ait.). 

Centric  leaves:  the  Austrian  Pine  (Pinus  Laricio,  Poir.),  the 
Showy  Lady's  Slipper  (Cypripedium  spectabile,  Salisb.),  the 
Wheat  (Triticum  vulgare,  Villars),  the  Adam's  Needle  (Yucca 
filamentosa,  L.),  the  Sweet  Flag  (Acorus  Calamus,  L.),  the 
Hyacinth  (Hyacinthus  orientalis,  Willd.),  and  the  Daffodil  (Nar- 
cissus Pseudo-narcissus,  L.). 

I.  BIFACIAL  LEAVES. — (1)  Let  the  leaf  of  Ficus  elastica  first 
be  studied.  The  leaf  being  leathery  and  firm  in  texture,  sections  of 
it  may  readily  be  made,  without  hardening  in  alcohol,  by  placing 
portions  of  it  between  flat  pieces  of  pith  and  cutting  through 
both  pith  and  leaf.  Specimens  which  have  laid  for  some  time  in 
alcohol  are  to  be  preferred,  because  they  have  been  rendered  more 
transparent  by  the  removal  of  the  chlorophyll.  The  sections 
would  better  be  made  transversely,  across  the  direction  of  the 
lateral  veins. 

A  section  may  be  mounted  in  a  drop  of  carbolic-acid  solution 
or  in  one  of  chloral  hydrate,  or,  if  the  leaf  had  previously  been 
treated  with  alcohol,  in  glycerin,  and  then  be  examined  first  with 
a  low  and  afterward  with  a  high  power. 

It  will  be  observed  that  the  epidermis  of  both  upper  and  lower 
surfaces  is  composed  of  three  tiers  of  transparent  cells ;  but  the 
upper  epidermis  is  thicker  than  the  lower,  by  reason  of  the  larger 
size  of  the  cells  in  its  two  inner  layers.  A  two-  or  more  layered 
epidermis  is  not  uncommon  among  the  leathery  evergreen  leaves 
of  warm  climates.  Probably  the  thickness  of  the  epidermis  both 
tempers  the  intensity  of  the  sun's  rays  and  retards  evaporation 
from  the  leaf. 

At  intervals  in  the  inner  tier  of  epidermal  cells  on  the  upper 
side,  and  more  rarely  on  the  lower,  are  very  large  cells  containing 
each  a  botryoidal  mass  attached  by  a  stalk  to  the  cell-wall  as 
shown  at  b,  Figure  1  (PI.  LXXXIIL).  This  mass  is  called  a 
cystolith.  Bodies  of  this  kind  arc  not  common  in  plants,  rarely 
occurring  outside  the  orders  Urticacew,  Acanthacese,  and  a  lew 
species  of  the  Cucurbitacese. 

Interior  to  the  upper  epidermis  are  seen  the  palisade  cells 
arranged  in  two  tiers.  In  both  tiers  the  cells  are  lengthened  in 
a  direction  perpendicular  to  the  epidermis,,  but  the  cells  of  the  ex- 


STUDY   OF    LEAF   STRUCTURE.  505 

terior  tier  are  considerably  longer.  The  cells,  it  will  be  observed, 
are  heavily  charged  with  chlorophyll  bodies. 

The  middle  portion  of  the  leaf  is  occupied  chiefly  by  a  very 
loosely  arranged  chlorophyll-bearing  parenchyma  consisting  of 
cells  which  are  ellipsoidal  in  form,  or  more  often  irregular  or 
even  branching,  the  cells  being  arranged  without  apparent  order. 
This  tissue,  next  the  lower  epidermis,  passes  into  a  parenchyma 
which  has  its  cells  somewhat  compactly  arranged,  but  still  not 
forming  a  palisade  tissue.  All  this  parenchymatous  portion 
included  between  the  palisade  tissue  and  the  lower  epidermis  is 
called  spongy  parenchyma.  Its  chlorophyll  bodies  are  not  nearly 
so  numerous  as  in  the  palisade  tissue ;  this  fact,  together  with  that 
of  the  less  compact  arrangement  of  its  cells,  accounts  for  the  much 
lighter  green  of  the  dorsal  surface  of  the  leaf. 

In  this  leaf  the  lower  epidermis  is  the  only  one  in  which  are 
found  stomata.  In  a  fortunate  section  which  cuts  one  of  the 
stomata  transversely  near  its  middle  the  appearance  will  be  as  at 
/  in  the  drawing.  The  guard-cells  are  so  shaped  as  to  form  a 
kind  of  ante-chamber  (/)  which  opens  by  a  narrow  passage  into 
a  large  air-chamber  (cf)  which  is  in  communication  with  the  inter- 
cellular spaces  throughout  the  leaf. 

An  effort  may  now  be  made  to  determine  the  chemical  nature 
of  the  cystolith.  For  this  purpose  a  fresh  section  may  be  mounted 
in  a  drop  of  water,  and  after  focusing  upon  a  cystolith  a  drop  of 
acetic  acid  may  be  placed  at  the  edge  of  the  cover  and  be  allowed 
to  run  under.  As  the  acid  comes  into  contact  with  the  cystolith 
effervescence  occurs  and  bubbles  of  gas  accumulate  in  the  cell, 
indicating  the  presence  of  calcium  carbonate.  After  effervescence 
ceases  the  cystolith  appears  to  the  eye  very  much  as  before,  except 
that  it  is  more  transparent. 

Removing  now  the  cover-glass,  washing  away  the  acetic  acid 
with  clean  water,  afterward  soaking  up  the  latter  with  blotting 
paper,  and  applying  two  or  three  drops  of  the  zinc-chloriodide 
iodine,  the  characteristic  blue  color'  due  to  cellulose  is  developed 
in  the  skeleton  of  the  cystolith  that  remains.  Cystoliths  usually, 
as  in  the  present  instance,  consist  of  a  cellulose  skeleton,  formed 
by  an  infolding  or  ingrowth  of  the  cell-wall,  encrusted  by  calcium 
carbonate.  The  latter,  however,  not  merely  forms  at  the  surface 
of  the  skeleton,  but  penetrates  its  mass. 


506  LABORATORY    EXERCISES    IN    BOTANY. 

Attention  is  also  directed  to  the  cross-sections  of  the  veins. 
These  are  seen  to  consist  chiefly  of  a  collateral  vasal  bundle  in 
which  the  phloem  faces  toward  the  lower  or  dorsal  side  of  the  leaf, 
and  the  xylera  toward  the  upper  or  ventral  side.  This  is  always 
the  case  in  leaves,  so  that  in  those  that  have  been  separated  from 
the  plant  or  in  those  that  have  become  twisted  on  their  petioles 
the  true  dorsal  or  ventral  side  may  be  determined  by  an  examina- 
tion of  the  bundle. 

A  cross-section  made  through  the  midrib  would  be  instructive 
as  showing  the  much  greater  prominence  of  the  rib  on  the  dorsal 
surface  of  the  leaf,  and  also  as  showing  a  vasal  bundle  with  its 
parts  much  better  developed  than  in  the  bundle  shown  in  Figure  1 
(PI.  LXXXIIL).  In  distinguishing  between  different  medicinal 
leaves  the  bundle  or  bundles  of  the  midrib  may  usually  be  ex- 
pected to  aiford  important  diagnostic  characters,  as  the  structure 
and  arrangement  of  the  bundles  often  differ  quite  widely  in  leaves 
of  different  species. 

(2)  A  bifacial  leaf  whose  structure  differs  considerably  from 
that  of  the  leaf  just  studied  is  the  pinuately-compound  leaf  of 
Cycas  revoluta.  Here  the  texture  is  also  coriaceous  and  firm,  and 
sections  may  be  made  as  before ;  but  in  order  to  comprehend  the 
structure  fully  it  will  be  necessary  to  make  sections  in  several 
different  directions. 

First  let  a  transverse  section  be  made  perpendicularly  to  the 
direction  of  the  midrib.  It  wrould  be  wise  to  cut  several  of  these 
sections,  so  that  one  may  be  found  sufficiently  thin  to  reveal  the 
structure  clearly.  The  thinnest  sections  are  then  transferred  to  a 
slide  and  treated  with  the  phloroglucin  reagent.  On  focusing 
upon  one  of  the  sections  with  the  low  power  an  appearance  will  be 
presented  which  is  illustrated  in  Figure  2  (PI.  LXXXIIL).  The 
leaflets  are  much  the  thickest  at  the  middle,  along  the  mid-vein, 
which,  as  usual,  is  most  prominent  on  the  lower  side,  and,  since 
the  leaflets  are  revolute,  the  thinner  portions  on  either  side  of  the 
mid-vein  appear  strongly  curved  when  viewed  in  section.  The 
upper  epidermis  is  thick-walled  and  single-layered.  The  exte- 
rior portion,  because  composed  of  cut  in,  does  not  stain  with  the 
phloroglucin,  while  tin-  remainder  of  the  wall  does  stain  quite 
strongly,  especially  in  old  leaves,  indicating  ligniiication.  The 
epidermis  is  supported  by  a  layer  (or  at  the  midrib  by  two  layer-) 


STUDY  OF  LEAF  STRUCTURE.  507 

of  thick-walled  cells  constituting  a  hypoderma.  Immediately  inte- 
rior to  the  hypodermal  tissue  is  a  single  layer  of  much  elongated 
palisade  cells.  The  second  layer  in  this  case  is  but  slightly  devel- 
oped. This  is  followed  still  farther  interior  by  a  spongy  parenchy- 
ma composed  of  thickish-walled,  somewhat  lignified,  and  strongly 
pitted  parenchyma.  The  cells  in  this  region,  nearly  midway  be- 
tween the  two  surfaces  of  the  leaf,  contain  little  if  any  chlorophyll, 
while  those  near  the  palisade  tissue  on  the  one  hand  and  the  lower 
epidermis  on  the  other  contain  chlorophyll,  though  in  less  quan- 
tity than  do  the  palisade  cells.  The  cells  are  all  regular  in  form, 
and  are  mostly  much  lengthened  in  a  direction  perpendicular  to 
the  midrib  and  parallel  to  the  epidermis. 

Focusing  up  and  down  on  this  tissue,  it  is  found  that,  like  other 
spongy  parenchyma,  it  is  very  loosely  arranged,  but  here  the  spaces 
are  larger  and  more  regular  than  in  the  leaf  of  Ficus  elastica. 

Next  the  lower  epidermis  is  an  interrupted  layer,  or  in  places 
two  layers,  of  chlorophyll-bearing  cells  which  are  slightly  elon- 
gated in  the  other  direction — namely,  perpendicularly  to  the  epi- 
dermis— thus  constituting  a  very  imperfectly  developed  palisade 
tissue.  The  interruptions  in  this  layer  are  the  places  where  the 
air-chambers  occur  over  the  stomata,  which  are  very  numerous 
between  the  midrib  and  the  margin  on  the  lower  surface,  but 
which  are  not  found  elsewhere  in  the  leaf. 

Examining  the  same  sections  with  the  high  power,  it  will 
be  found  that  the  stomata  located  in  the  single-layered  epi- 
dermis present  some  striking  peculiarities.  Referring  to  Plate 
LXXXIV.,  the  air-chamber  over  one  of  the  stomata  is  shown  at 
/,  and  an  exterior  opening  at  h.  This,  however,  is  not  the  stoma 
proper,  but  is  rather  the  opening  into  a  vestibular  cavity  which 
leads  to  the  storna  above.  A  favorable  section  shows  the  guard- 
cells  as  indicated  in  the  drawing.  Where  they  meet,  as  at  i,  there 
is  an  excessive  thickening  which  is  also  strongly  lignified,  while 
the  rest  of  the  wall  remains  relatively  thin,  and  that  portion  which 
faces  the  vestibular  cavity  is  wholly  unliguified. 

The  cells  bounding  the  vestibular  cavity  are  long  cells,  pointed 
at  their  exterior  ends  and  curved,  and  so  placed  as  to  form  a  dome- 
shaped  prominence  in  the  lower  epidermis,  the  dome  being  per- 
forated at  the  top  by  a  rounded  aperture.  The  arrangement  of 
these  cells  will  be  understood  better  by  reference  to  Figure  1 


508  LABORATORY    EXERCISES    IN    BOTANY. 

(PL  LXXXVL),  ill  which  6  represents  a  vestibular  cell,  and  ft  the 
vestibular  aperture.  The  section  from  which  the  drawing  was 
made  was  prepared  by  shaving  off  a  portion  of  the  epidermis, 
cutting  just  beneath  it  parallel  to  the  surface. 

In  Figure  2  (PL  LXXXVL)  the  section  passed  through  the 
epidermis  itself,  parallel  to  and  near  the  surface,  cutting  off  the 
dome-cells  near  their  bases  and  exposing  the  stoma.  The  latter 
presents  no  especial  peculiarities  except  the  strong  bracing  at 
the  ends  of  the  guard-cells,  preventing  all  movement  in  the 
direction  of  the  length  of  the  stoma.  It  will  readily  be  seen, 
by  comparing  this  with  the  sectional  view  in  Figure  3,  that  any 
movement  of  expansion  must  cause  the  guard-cells  to  bow  out 
in  the  middle,  thus  enlarging  the  aperture  between  them. 

A  section  of  the  leaflet  made  parallel  to  the  midrib  and  per- 
pendicular to  its  upper  and  lower  surfaces  is  also  instructive  in 
many  ways.  Such  a  section  is  shown  in  Figure  1  (PL  LXXXV.). 
The  hypodermal  cells  are  here  seen  to  be  much  elongated  and 
even  fibrous  in  their  character;  and  that  the  spongy  parenchyma 
is  composed  of  plates  of  elongated  cells  with  large  intercellular 
spaces  between  the  plates  is  now  clearly  seen  by  comparison  with 
Figure  3. 

A  quite  unusual  thing  in  leaf  structure  is  the  fact  that  in  the  leaf 
of  Cycas  so  large  a  proportion  of  the  cells  of  the  mature  leaf  are  lig- 
nified  and  pitted.  This  is  true  even  of  the  epidermal  cells  (except, 
of  course,  the  cuticle)  and  of  the  cells  of  the  mesophyll  (except 
the  palisade  tissue) ;  but  even  this  tissue  possesses  strongly-thick- 
ened vertical  bands  in  the  walls  of  its  cells,  many  of  which  bands 
are  lignified.  A  section  cut  across  the  longer  diameter  of  the  pali- 
sade cells  shows  this  fact  beautifully.  Figure  2  (PL  LXXXV.) 
represents  a  few  palisade  cells  as  seen  in  such  a  section  :  a  is  an 
intercellular  space;  6,  a  lignified  thickening;  c,  an  unthickened 
portion  of  the  cell-wall.  The  portion  from  which  the  illustration 
wa<  drawn  consisted  of  cells  more  compactly  arranged  than  most 
of  the  cells  of  this  tissue,  but  even  in  the  more  loosely  arranged 
cells  the  walls  possess  thickenings  similar  to  those  in  the  drawing. 

II.  CENTRIC  LEAVES. — Let  the  centric  type  of  leaf  structmv 
be  exemplified  in  cross-sections  of  the  leaf  of  Pinus  Laricio,  not 
uncommonly  cultivated  in  this  country  under  the  name  of  "Aus- 
trian Pine." 


STUDY    OF    LEAF   STRUCTURE.  509 

Good  sections  are  easily  made,  either  of  fresh  or  of  alcoholic 
material,  by  cutting  the  leaves  between  pieces  of  pith.  In  order 
to  understand  the  structure  well,  it  is  advisable  to  clear  the  sec- 
tions by  means  of  carbolic  acid,  or,  better,  by  treating  them  with 
Labarraque's  solution  until  colorless,  washing  them  thoroughly 
and  double-staining — say  with  iodine-green  and  ammonia  car- 
mine— and,  after  anhydrating,  mounting  them  in  balsam. 

The  sections  are  nearly  straight  on  one  edge  (the  ventral,  as 
will  be  shown  by  studying  the  bundles)  and  strongly  curved, 
nearly  semicircular,  on  the  other.  The  excessively  thick-walled 
and  one-layered  epidermis  is  punctured  at  frequent  intervals,  as 
well  on  the  ventral  as  on  the  dorsal  surface,  by  stomata.  Beneath 
the  epidermis  is  a  hypoderma  composed  of  two  or  three  layers  of 
thick-walled  fibrous  cells  interrupted  only  where  the  stomata 
occur.  Interior  to  this  hypoderma,  on  both  sides  of  the  leaf,  is 
a  peculiar,  thin-walled,  chlorophyll-bearing  parenchyma.  The 
walls  of  its  cells  are  thrown  into  numerous  folds  which  project 
into  the  cell-lumen.  Arranged  at  nearly  equal  intervals  in  this 
parenchyma,  around  the  axial  portion  of  the  leaf,  are  from 
four  to  six  secretion-reservoirs  in  which  the  circle  of  secreting 
cells  is  ensheathed  by  one  of  thick-walled  cells. 

The  axial  portion  of  the  leaf  is  separated  from  the  rest  by  a 
distinct  sheath  of  rather  large  and  not  very  thick-walled  cells, 
interior  to  which,  and  surrounding  a  pair  of  collateral  vasal 
bundles,  are  several  layers  of  parenchyma-cells  possessing  bor- 
dered pits  similar  to  those  of  the  tracheids  so  characteristic  of 
the  woody  portions  of  gymnosperms. 


STUDY   OF    LEAF   STRUCTURE. 


511 


PLATE  LXXXIIL,  FIG.  1— Small  portion  of  Cross-section  of  Leaf  of  Ficus  elastica, 
illustrating  a  bifacial  leaf  (magnification,  150  diameters);  a,  upper  epidermis;  b,  cysto- 
lith  in  an  extra  large  epidermal  cell ;  c,  palisade  parenchyma;  d,  spongy  parenchyma; 
e,  lower  or  dorsal  epidermis ;  /,  stoma ;  g,  air-chamber  above  stoma ;  h,  xylem  of  a  small 
bundle  ;  t,  soft  bast  of  the  bundle  ;  k,  hard  bast  or  bast-fibres. 

FIG.  2.— Portion  of  Cross-section  of  Leaf  of  Cycas  revoluta  (magnified  40  diameters) : 
a,  epidermis:  b,  hypoderma ;  c,  palisade  tissue;  d,  spongy  parenchyma;  e,  stoma;  /, 
xylem  of  bundle  constituting  the  midvein ;  g,  phloem  of  the  same. 


STUDY   OP   LEAF   STKUCTUKE. 


513 


PLATE  LXXXIV.— Small  portion  of  the  Cross-section  of  the  Leaflet  of  Cycas  revoluta 
(magnified  210  diameters) :  a,  cuticle ;  6,  epidermal  cells ;  c,  hypoderma ;  d,  palisade 
parenchyma ;  e,  pitted  cells  in  middle  portion  of  spongy  parenchyma,  which  contain 
few  if  any  chloroplasts  ;  /,  air-chamber  above  stoma ;  g,  ordinary  epidermal  cell  of  lower 
epidermis ;  h,  opening  into  vestibular  cavity  of  stoma ;  i,  a  stoma  ;  k,  vestibular  cavity. 
31 


STUDY   OF   LEAF   STRUCTURE.  ' 


515 


£   T,    LXXXV.,  FIG.  1.— Small  portion  of  section  of  Leaflet  of  Cycas  revoluta,  made 

vertically  through  the  leaflet  parallel  to  the  midrib  (magnified  210  diameters) :  a,  cuticle ; 

0.  epidermis  ;  c,  hypoderma  ;  d,  palisade  parenchyma;  e,  imperfectly  developed  second 

Jt  palisade  cells;  /,  spongy  parenchyma;  g,  large  air-space  between  plates  of  spongy 

parenchyma ;  h,  ordinary  epidermal  cell  of  lower  epidermis ;  i,  vestibule  of  stoma. 

FIG.  2— A  few  Palisade  Cells  of  Cycas  leaf  cut  perpendicular  to  their  longest  diame- 
ter :  a,  intercellular  space  ;  b,  lignifled  thickening ;  c,  ordinary  thin  portion  of  wall. 
(Magnification,  330  diameters.) 


STUDY   OF   LEAF   STRUCTURE. 


517 


'v 


PLATE  LXXXVL,  FIG.  1.— View  of  small  portion  of  Lower  Epidermis  of  Cycas  leaf  as 
seen  from  below  (magnified  330  diameters) :  6,  one  of  the  cells  forming  the  dome-shaped 
vestibule  of  the  stoma  (the  outer  ends  of  the  cells  are  strongly  cutinized  and  their  walls 
are  pitted) ;  a,  vestibular  opening;  c,  ordinary  epidermal  cell  (its  walls  are  also  pitted). 

FIG.  2— Small  portion  of  Epidermis  from  lower  side  of  Cycas  leaf,  cut  parallel  to  and 
near  the  surface,  opening  the  vestibular  cavity  so  as  to  show  the  stoma  (magnification, 
330  diameters) :  a,  ordinary  epidermal  cell ;  b,  base  of  one  of  the  vestibular  cells  ;  c,  one 
of  the  guard-cells  ;  d,  strong  lignified  thickening  at  the  end  of  the  stoma. 


STUDY   OF    LEAF  STRUCTURE. 


519 


INDEX. 


ABRONIA,  embryo  of,  245 
Absorption  by  roots,  24 
Acacias,  Australian,  108 
Acer  dasycarpum,  31,  101,  229,  491 

leaf  of,  101 
saccharinum,  89 

Acetic  methyl-green  solution,  272 
Acid,  acetic,  as  reagent,  260 
in  study  of  crystals,  432 
carbolic,  as  reagent,  262 
use  in  mounting,  277 
chromic,  as  reagent,  260,  336 

in  study  of  cork,  336 
formic,  as  reagent,  261 
fuchsin  in  study  of  amyloplasts  and 

crystalloids,  400 
glacial  acetic,  as  reagent,  260 
hydrochloric,  as  reagent,  259 
in  study  of  crystals,  432 
with  phloroglucin,    20,   270,  301, 
315,   346,   379,   449,   457,   458, 
492,  493 

nitric,  as  reagent,  260 
osmic,  as  reagent,  261,  409 

in  study  of  crystalloids,  409 
picric,  as  reagent,  261 
sulphuric,  as  reagent,  258,  286 
and   iodine,  as  test  for  cellulose, 

286 

sulphurous,  as  reagent,  259 
Aconitum  Napellus  (Monkshood),  57, 

125,  477 
Acorus  Calamus  (Sweet  Flag),  45,  197, 

429,  449,  467,  504 
rhizome,  section  of  (illustration), 

435 
Adam's   Needle   (Yucca   filamentosa), 

centric  leaf  of,  504 
Adder's  Tongue  (Erythronium  Ameri- 

canum),  69, 181 
Adhesion,  151,  187,  188 
Adiantum,  leaflet  of,  91,  95;  illustra- 
tion, 95 

capillus-veneris,  89 
pedatum,  89 
Adlnmia  cirrhosa,  131 
Adnation,  151,  187,  188 
Adventitous  roots,  24 


JSsculus  Hippocastanum  (Horse-chest- 
nut), 31 

^Estivation,  vexillary,  150 
Agapanthus,  epidermis  of,  319 
Aggregated  fruits,  204 
Agrimonia  parviflora,  101 
Ailanthus,  leaf-scars  of,  42 

pitted  ducts  in,  358 
Air-spaces,  intercellular,  study  of,  439 
Alse  or  wings,  150 
Alcannin  solution,  19,  275 

as  stain  for  cutinized  walls,  330 
as  test  for  oleo-resins,  442 
in  study  of  fixed  oils,  409 
Alcohol,  acid,  uses  of,  259 
as  reagent,  262 
in  coagulating  latex,  387 
in  study  of  iuulin,  423 
uses  of,  264 

Aleurone-grains,  study  of,  407 
of  Kicinus  (illustration),  411 
Algae,  stain  for,  274 
Alisma  Plantago,  241,  439,  457 
Allamanda,  coloring  matter  in  flowers 

of,  416,  417 

Allium  Cepa,  69,  283,  467 
cernuum,  69,  181 
sativum,  69 

I  Almond,  seed  of,  229 ;  illustration,  233 
j  Alternate  phyllotaxy,  40 
|  Althsea  oificinalis,  429,  435 

section  of  root  (illustration),  435 
|  Alum,  am monio- ferric,  as  reagent,  266 
I  Amaryllis  Atamasco,  69 
bulb  of,  283 
epidermis  of,  319 
formosissima,  69,  70,  429,  467,  477 

bulb  of  (illustration),  73 
mucilage-  and  crystal-sacs  in,  429 
radial  bundle  in  root  of,  467 
roots  of,  477 

Amelanchier  Canadensis,  211 
Ament,  138 
American  Beech,  39 
Mountain  Ash,  101 
Ammonia  carmine,  271 
Ammonio-ferric  alum  as  reagent,  266 
Amygdalus  persica,  229,  425 
521 


522 


INDEX. 


Amyloid,  detection  of,  260 
Amyloplasts  in  potato,  398,  400 

staining  <>!',  -7- 

Anacyclus  Pyrethrum,  423,  439 
Ananassa  sativa,  223 
Androecium,  118, 144, 158, 164, 176, 182, 
189,  191 

of  Cypripedium,  191 

of  Erythronium,  182 

of  Narcissus,  189 
Andromeda  mariana,  1 63 
Angiosperma?,  244 
Anhydration  of  tissues,  265 
Anilin  chloride  as  reagent,  270,  441 
and  HC1  as  test  for  lignified  walls, 
441 

in  balsam  mounting,  267,  277 

oil.     See  Anilin. 
Anilin-blue  as  stain  for  callose,  381 

solution  as  stain,  272 
Animal  selection  in  the  development 

of  fruits,  206 
Annular  ducts  of  Pelargonium  zonale, 

354 

Anteposition  of  floral  organs,  120 
Anthers,  innate,  127,  139 

introrse,  139 

lateral,  127 
Anthotaxy,  centrifugal,  138 

centripetal,  138 

determinate,  137 

in  Arabis  lyrata,  198 

in  Composite,  169 

indeterminate,  137 
Anthoxanthin,  416 
Apios  tuberosa,  57 
Apocarpous  fruits,  203 
Apocynum  androsaemifolium,  387 
root-bark  of,  313 

cannabinum,  387 
Apparatus,  accessory,  255 

care  of,  21 
Apple,  144,  211,  229,  313,  335,  425 

flower  of,  144 

sugar  in,  425 

tree,  cork -tissue  of,  335 

twig  of,  313 
Aquatics,  leaves  of,  102 
Aquilcnia  ( 'anadensis,  125 
Arabis  lyrata,  137;  illustration,  141 
Aracese,  trichoblasts  in,  440 
Aralia  nudicaulis,  439,  441,  445 

secretion-reservoirs  of,  441 ;  illus- 
tration, 445 

ra.vinnsa,  307,  439 

s|>im>sa,  leal-scars  of,  42 
Arbutus,  Trailing  (illustration),  167 
Arctimn  Lappa,  23,  169,  42:5. 
Arrtostaphylus  uva-ursi,  16:5 


Arethusa  bulbosa,  187 
Argemone  Mexicana,  131 
Arisaema  Dracontium,  65,  197,  432 

mucilage-  and  crystal-sacs  in,  432 
triphyllum,  65,  92, 197,  201,  439, 467, 

477,  491 ;  illustration,  201 
leaf-venation  of,  92 
Aristolochia  Sipho,  175,  457,  491 
Arrow  Arum,  197 
Arrow-head,  air-spaces  in,  439 

closed  collateral  bundles  of,  457 
Arum  family,  leaf-venation  in,  92 
Asarum  Canadense,  175,  179;  illustra- 
tion, 179 
Asclepias  cornuti,  203,  387,  393 

stem-sections   showing    latex-cells 

(illustration),  393 
purpurascens,  387 
tuberosa,  root-bark  of,  313 
Ash,  31,  40,  43 

twig  of  (illustration),  43 
twigs  of,  40 
Asimina  triloba,  301,  313 

bark  of,  313 

Asparagus  officinal  is,  491 
Aspidium  acrostichoides,  83,  89 
Filix-mas,  357,  448,  491,  503 

scalariform  ducts  of,  357 
marginale,  357,  448,  491 

scalariform  ducts  of,  357 
spinulosum,  491 
Thelypteris,  491 
Atamasco  Lily,  69 
Austrian  Pine,  centric  leaf  of,  504 
Avena  sativa,  241 
Axillary  buds,  31 
Azalea,  83 

BALD  CYPRESS,  bast-fibres  of,  367 
stem  of,  492 
tracheids     of,     359 ;     illustration, 

365 

Balsam  as  mounting  medium,  275 
Poplar,  31,  39,  40,  43,  335 
corky  tissue  of,  335 
twig  (illustration),  43 
twigs  of,  40 
Banana,  leaf- venation  of,  92 

sugar  in,  4'J"> 
Barberry  family,  flowers  of,  121 

leaves  of,  7-~> 
Bark,   inner,  how  distinguished  from 

middle,  !>"> 
layers  of,  25,  34 
Barley,  24 1 
r,a>s\vood,  31,  39,  40,  43,  101,  335,  367, 

379,  429,  457 

twig  of,  40;  illustration, 43 
l>ast-fil>ivs,  branching,  309 


INDEX. 


523 


Bast-fibres  of  Cinchona  Calisaya  (illus- 
tration), 377 
of  Hickory,  34 

of  Larix  Europsea  (illustration),  375 
of    Silphium    laciniatum    (illustra- 
tion), 373 
study  of,  367 
Beach  Pea,  107 
Bean,  Castor,  101,  235,  239  ;  illustration, 

239 

Bearberry,  163 
Beech,  39,  43,  83,  89,  504 
American,  39 
bifacial  leaf  of,  504 
pre foliation  of,  83 
twig  (illustration),  43 
twigs  of,  39 
Beet,  roots  of,  477 
Beggar-ticks,  169 

Begonia,  89,  307,  311,  319,  433,  503 
bifacial  leaf  of,  503 
crystals  in,  433 
discolor,  503 

collenchyma  of,  307,  311 
epidermis  of,  319 
nitida,  89 
Bellwort,  89,  181 
Berberidacese,  flowers  of,  119 
Berry,  definition  of,  224 
Bertholletia  excelsa,  407 
Beta  vulgaris,  425,  477 
Bi-collateral  bundles,  460 
Bidens  frondosa,  169 
Bird  Cherry,  flowers  of,  143,  147 
Birthwort,  211 

Bismarck  brown  as  stain  for  secretion- 
cells,  459 

Bitter  Dock,  dotted  ducts  in,  358 
Bitternut  Hickory,  32 
Bittersweet,  cork -tissue  of,  335 

open  collateral  bundles  of,  457 
Black  Cohosh,  radial  bundle  in  root  of, 

467 

roots  of,  477 

stem  of,  491 

Currant,  32,  335 

corky  tissue  of,  335 
Mustard,  137,  211 
Pepper,  235,  236,  237,  239 
drupe  of  (illustration),  239 
seed,  235,  236,  237 
Blackberry,  143 
Bladderwort,  107 
Bleaching  agents,  267 

tissues,  267 

Bloodroot,  131,  135,  390,  429 
flowers  of,  131,  135 
plant  (illustration),  135 
resin  sacs  or  secretion-cells  in,  390,429 


Blue  Cohosh,  45 

Flag,  45,  83,  211,  448,  477 
concentric  bundles  of,  448 
roots  of,  477 

Violet,  211 
Blueberry,  163 
Bluets,  157 

Bordered  pits  of  gymnosperms,  360 
Borraginacese,  callose  in  seeds  of,  382 
Botrychium  Virgin  ianum,  467 
Boussingaultia  baselloides,  57 
Bouvardia,  159,  161 

twig  of  (illustration),  161 
Brake,  Common,  concentric  bundles  of, 

448 
Brassica  nigra,  137,  211 

Sinapistrum,  137 

Brazil-nut,  aleurone-grains  of,  407 
Broom,  149 

Brushes,  camel's-hair,  256 
Bryum  roseum,  89,  283 
Buckwheat/  175 
Bud,  structure  of,  32 
Buds  and  bulbs  compared,  70 
Bud-scales.  32,  33,  42 

uses  of,  33 
Bulbils,  70 
Bulbs,  67,  70,  73 ;  illustrations,  73 

resemblance  to  buds,  70 
Bulrush,  air-spaces  in,  439 

closed  collateral  bundles  of,  457 
Burdock,  23,  169,  307,  423 

inulin  in,  423 
Bur-reed,  air-spaces  in,  439 
Buttercup,  120,  126,  144,  145,  203,  477 

flower  of,  120,  126,  144,  145 

roots  of,  477 

Butterfly-weed,  root-bark  of,  313 
Butternut,  pitted  ducts  in,  358 
Butterwort,  107 

CACTACEJE,  flowers  of,  119 
Cactus,  leaves  of,  75 
Caducous  calyx,  132 
Calamagrostis  longifolia,  477,  478,  483 
roots  of,  478 

root-tip  of  (illustration),  483 
Calcium  carbonate,  recognition  of,  259, 

260 
Calcium-oxalate  crystals  as  affected  by 

H2S04,  259 
of  Begonia,  308 
recognition  of,  260,  308,  432 
Calla  Lily,  89,  92,  197 

leaf-venation  of,  92 
palustris,  197 
Calladium  esculentum,  65 
Callisia  repens,  89;  illustration,  97,  99 
Callose,  blue  stain  for,  272 


524 


INDEX. 


Callose,  chloro-zinc-iodine  test  for,  264 

in  sieve-tissue  of  Pumpkin,  380 

nature  of,  382 

recognition  of,  262 

red  stain  for,  274 
Calopogon  pulchellus,  187 
Caltha  palustris,  125,  203 
Calyx,    118,   126,  143,  157,  163,  170, 

176,  177 

Catnassia  Frazeri,  69,  181 
Cambium  zone  in  roots,  480 
Camellia,  flowers  of,  120 

leaves  of,  313 
Camera  lucida,  Abbess,  257 

use   in   determining    magnifying- 

power,  254 
use  in  drawing,  277 
Campanula  rotundifolia,  157 
Camptosorus,  venation  of,  91 
Canadian  Hemp,  laticiferous  tissue  in, 

387 

Cane-sugar  in  Carrot,  426 
Canna,  crystalloids  in,  410 

edulis,  241 

seeds  of,  241 

Capsella  bursa-pastoris,  101 
Capsule  of  Poppy,  212 
Carbolic  acid  as  reagent,  262 

use  in  clearing,  504 
Cardamine  rhomboidea,  137 
Carina,  150 
Carpel,  118 
Carpophore,  217 
Carrot,  air-spaces  in  stem  of,  439 

roots  of,  23,  477 

sugar  in.  425 
Caruncle,  235 
Carya  alba,  31,  327 
Caryopsis,  241 

Cascara  Sagrada,  crystal-sacs  in,  429 
Cassandra  calyculata,  163 
Castanea  sativa,  var.  Americana,  89, 

335 

Castor  Bean,  101,  235,  297,  407 
aleurone-grains  of,  407 
illustration,  239 
seed,  235 
Catkin,  138 

Caulophyllum  thalictroides,  45 
Celandine,  101,  131,  211,  387,  390 

laticiferous  tissue  in,  387,  390 
Cell,  the  typical  vegetable,  283 
Cells,  separation  of,  by  chromic  acid, 260 
Cellulose,  blue  stain  for,  272 

chloro-zinc-iodine  test  for,  263,  287 

dissolved  by  strong  H2SO4,  258 

in  cystolith,  505 

iodine  and  sulphuric  acid  test  for, 
263 


Cellulose,  recognition  of,  261,  262 

solvent  for,  269 

sulphuric  acid  and   iodine  test  for, 

286 

Centric  leaf  of  Austrian  pine,  508 
Centrifugal  anthotaxy,  138 
Centripetal  anthotaxy,  138 
Ceylon  Cinnamon,  bark  of,  313 
Chalaza,  229,  235 
Chara,    protoplasmic    movements    in, 

331 

Charlock,  137 

Chelidonium  rnajus,  101,  131,  211,  387 
Cherry,  83,  143,  147,  203,  205,  207,  209 

flower  of  (illustration),  147 

fruit  of,  203,  205 ;  illustration,  209 

seed  of,  207 
Chestnut,  89,  335 

corky  tissue  of,  335 
Chicory,  169,  387,  423,  427 

inulin  in,  423 

laticiferous  tissue  in,  387 

root,  inulin- crystals  in  (illustration), 

427 

Chimaphila  umbellata,  163 
Chloral  hydrate  for  clearing,  328 
Chloral-hydrate  iodine  as  reagent,  264 
in  study  of  chloroplasts,  415 

solution,  uses  of,  265,  267,  504 
Chloriodide-of-zinc  iodine   as  reagent, 

263,  329,  336,  431 
for  detection  of  cutin,  329 
Chlorophyll,  75,  414 

bodies,  study  of,  264,  413 
Chloroplasts,  300,  413,  414,  419,  421 

division  of,  414 

functions  of,  414 

of  moss  leaf  (illustration),  419,  421 

study  of,  413 

Choripetalous  flower,  133 
Christmas  Rose,  144 
Chrysanthemum  Leucanthemum,  169 
Cichorium  Intybus,  169,  387,  423 
Cinchona,  bast-fibres  of,  369 

Calisaya,  367 

bast-fibres  of  (illustration),  377 

tree,  157 

Cimicifuga    racemosa,    467,   477,   479, 
481,  485,  487,  489,  491 

roots  of,  479,  481 

section  of  root  of  (illustrations),  485, 

487,  489 

( 'innanioinum  Zeylanicum,  bark  of,  313 
Cinnamon,  Ceylon,  bark  of,  313 

leaf  of,  venation  of,  93 
Cinquefoil,  101,  143 
Citrullus  vulgaris,  379 
Citrus  Aurantium,  211,  229,  439 

Limonum,  211 


INDEX. 


525 


Cladophora  glomerata,  283 
Claytonia  Virginica,  57 
Cleanliness,  importance  of,  in  micros- 
copy, 279 

Clearing  by  means  of  acetic  acid,  260 
of  chloral-hydrate  solution,  264 
of  phenol,  262 

Clematis  Virginiana,  457,  491 
Climbing  Fumitory,  131 
Clintonia  borealis,  89 
Clover,  leaf  of,  84,  101 

prefoliation  of,  84 
Cloves,  83 

Club-moss  type  of  stem,  491,  493 
Cobsea  scandens,  leaf-venation  of,  92 
Cocculus  Carolinus,  stem  of,  491 
Cocoanut,  313 

Palm,  241 
Cocos  nucifera,  241 
Coffee  tree,  157 
Cohesion,  150,  151,  187 
Colchicum  auturnnale,  65,  211,  215,  401 

starch  of,  401 

capsule  of  (illustration),  215 
fruit  of,  211 
Coleorhiza,  242 

Collateral  bundles,  study  of,  457 
Collenchyrna  of  Begonia  petiole,  311 

study  of,  307 

Coloring  matters,  study  of,  413 
Columbine,  125 
pistils  of,  127 

Column  of  Cypripedium,  191 
Common  Hyacinth,  69 

Milkweed,  laticiferous  tissue  in,  387 
Salsify,  laticiferous  tissue  in,  387 
Companion-cells,  379 
Comparison,  value  of,  in  classification, 

199 

Compass  Plant,  bast-fibres  of,  367 
dotted  ducts  in,  358 
secretion-reservoirs  in,  439 
Complete  flower,  133 
Composite,  27,  169,  171 
contain  inulin,  27 
flowers  of,  169 
Concentric  bundle  of   Pteris  aquilina 

(illustration),  453 
of    Smilacina    rhizome    (illustra- 
tion), 455 

bundles,  study  of,  447,  453,  455 
Connecting-links,  199 
Continental    microscope    (illustration), 

251 

Convallaria  majalis,  45,  89 
Convolvulus  batatas,  425 

sepium.  157 

Coptis  trifolia,  125,  129,  203;  illustra- 
tion, 129 


Coralline  solution,  274 
Cordate  leaves,  78 
Coriaceous  leaves,  79 
Coriander,  211,  217,  221 

fruit  of,  217  ;  illustrations,  221 
Coriandrum  sativum,  211 
Cork  and  cutin,  uses  of,  to  plant,  338 

development  of,  335,  337 

formation  of,  in  Pelargonium  zonale 

(illustration),  343 
in  Solanum    Dulcamara   (illustra- 
tion), 343 
Corms,  study  of,  65,  67 ;  illustrations, 

67 
Corn,  vasal  bundles  of,  457 

Cockle,  211 

Yellow  Dent,  grain  of  (illustrations), 

247 

Corn  us  florida,  bark  of,  313 
Corolla,   118,  126,  143,  157,  164,  182, 
190 

of  Cypripedium,  190 
Corona,  nature  of,  in  Narcissus,  188 
Corydalis  glauca,  131 
Corymb,  138 

Costate-reticulate  leaf,  93 
Cover-glasses,  256 

Cow  Parsnip,  air-spaces  in  stem  of,  439 
Crab-apple,  211 
Cranesbill,  45,  101,  117,  211 

tannin-sacs  in,  430 
Creeping  Crowfoot,   radial  bundle  in 

root  of,  467 
Cremocarp,  217 
Cress  family,  leaves  of,  101 
Crocus  sativus,  65 

vernus,  65 
Crosnes,  57 
Cross-fertilization  in  Composites,  171 

in  Houstonia,  158 

in  Sweet  Pea,  151,  152 
Croton  Oil  Plant,  235 

Tiglium,  235,  407 

Crown  of  root,  its  real  nature,  23,  28 
Cruciferse,  101,  119,  139,  140 

flowers  of,  119 

leaves  of,  101 
Cruciferous  flower,  its  structure,  137, 

141 
Crystalloids  in  Castor  Bean,  408 

in  Potato  (illustration),  403 

recognition  of,  263 

staining  of,  401 

study  of,  269 

Crystals   in   corolla  of  Linaria,   417; 
illustration,  421 

in  latex  of  Milkweed,  389 
Crystal-sacs,  429 
Cucumber,  211 


526 


INDEX. 


Cucumber,  Wild,  bi-collateral  bundles 

of,  457 
Cucumis  Melo,  425 

sativus,  211 

Cucurbita  citrullus,  229 
maxima,  379,  457 
Pepo,  229,  358,  379,  457,  465,  491 
bi-collateral   bundle   of    (illustra- 
tion), 465 

Cucurbitaceae,  bundles  of,  457 
Cultivated  lilies,  epidermis  of,  319 
Culver's  Root,  radial  bundle  in,  467 
rhizome  of,  45 
rootlets  of,  477 

Cuprammonia  as  reagent,  269 
Cuscuta,  embryo  of,  273 
Custard  Apple,  bark  of,  313 
Cuticularized  or  suberized  tissues,  rec- 
ognition of,  259,  262,  270,  272, 
275 

staining  of,  272,  275 
Cyanin  as  test  for  oleo-resin,  275,  442 

in  study  of  fixed  oils,  409 
Cycas  revoluta,  301,  503,  506,  511,  513, 

515 

leaf  of,  506 

pitted  parenchyma  of.  301 
sections  of  leaf  of  (illustrations), 

511,  513,  515 
Cylinder-sheath,  51 
Cypripedium  acaule,  187, 190, 195,  211 ; 

illustration,  195 
pubescens,  187,  467,  477 
spectabile,   187,  467,  469,  473,  475, 

477,  504 
radial  bundle  in  root  of,  467,  469 ; 

illustrations,  473,  475 
Cystoliths,  504,  505 

callose  in,  382 
Cytisus  scoparius,  149 

DAFFODIL,  69,  187,  504 

centric  leaf  of,  504 
Daisy,  Ox-eye,  169 
Dandelion,  22,  23,  101,  102,  105,  169, 

387,  389,  395,  423 
inulin  in,  423 

laticiferous  tissue  in,  387,  389;  illus- 
tration, 395 

leaf  of,  101,  102;  illustration,  105 
root  of,  22;  illustration,  23 
Daphne  Mezereum,  367 
Darlington  ia.  108 

Darwin,  (  harlcs,  observations  on  dimor- 
phism. 158 
on  Sundew,  111 
on  Sweet  Pea,  153 
Date  Palm,  241 
Datura  Stramonium,  157,  211,  235 


Daucus  Carota,  23,  425,  439,  477 
Decussate  leaves,  41 
Dehiscence,  circumscissile,  213 

loculicidal,  212 

of  Pea  pod,  204 

of  Poppy  capsule,  212 

septicidal,  212 

septifragal,  213 
Delphinium  consolida,  125 

Staphisagria,  235,  407 
Dentaria  laciniata,  57,  137 
Dermatogen,  478 
Determinate  anthotaxy,  137 
Deutzia  scabra,  89,  92,  99 
leaf  of  (illustration),  99 
leaf-venation  of,  92 
Deviations  from  typical  flower,  119 
Dewberry,  143 
Diadelphous  stamens,  151 
Dicentra  cucullaria,  131 
Dicotyls  and  gymnosperms,  secondary 
changes  in  roots  of,  481 

leaf-venation  of,  93 

roots  of,  477 

type  of  stem,  491,  495 

typical  flower  of,  117 
Digestion  in  Sundew,  111 
Dimerous  flower,  133 
Dimorphous  flowers,  158, 159 
Dioacism  of  Trailing  Arbutus,  164 
Dionfea,  leaves  of,  75,  107 

muscipula,  107 
Dioscorea  villosa,  89 
Diphenylamin  solution,  265,  267 
Disk-flowers  of  Composite,  170 
Dispersion  of  Fig,  225 

of  Lemon,  219 

of  Poppy,  213 

of  seeds  of  Pea  and  Cherry,  206 

of  Wintergreen,  224 
Dissecting  microscope,  18 
Dividers,  draughtsman's,  257 
Dog  Hose,  143 
Dogbane,  laticiferous  tissue  in,  313,  387 

root- bark  of,  313 
Dotted  or  pitted  duct,  358 
Double  staining,  272,  274,  302,  357, 367, 

450,  509 

Gram's  method,  274 
of  bast-fibres,  367 
with  gentian-violet  and  eosin,  302, 

450 
with   iodine-green    and   ammonia 

carmine,  509 
and  eosin,  357 
Dracaenas,  stems  of,  495 
Drawing  microscopic  objects,  277 
Dried  material,  treatment  of,  20 
Drosera  intermedia,  var.  Americana,! 07 


INDEX. 


527 


Drosera  rotundifolia,  107,  110,  113 

Drupe,  206 

Duckweed,  23 

Ducts  of  Pelargonium  zonale,  351 
pitted  (illustration),  363 
reticulate  (illustration),  355 
scalariform,  357  ;  illustration,  363 
spiral  (illustration),  355 

Dutchman's  Breeches,  131 

Pipe,  open  collateral  bundles  of,  457 

EAST  INDIAN  PITCHER-PLANT,  107 
Echinocystis  lobata,  457 
Eel-grass,  chloroplasts  of,  413 
Elder,  bast-fibres  of,  367 

cork-tissue  of,  335 
Elecampane,  inulin  in,  423 
Elm,  slippery,  bast-fibres  of,  367 
Elodea  Canadensis,  413 
Embryo,  monocotyledonous,  241 

of  Abronia,  245' 

of  Cuscuta,  245 

of  Lemon,  245 

polycotyledonous,  244 
Endodermis,  447,  450,  469 

of  radial  bundle  of  Cypripedium  spec- 

tabile,  469 

Endophloeum,  26,  60,  496 
Endorhizal  germination,  243 
Endosperm,  229,  230,  237 
Entomophilous  flowers,  143 
Eosin  solution,  272 
Epicotyl,  243 
Epidermal  appendages,  study  of,  327 

tissue,  study  of,  319 

Epidermis  of  corolla-spur  of  Linaria 
(illustration),  421 

of  leaf,  77 

of  Cycas  revoluta  (illustration),  517 

of  Tulip  leaf  (illustration),  325 

structure  of,  323 
Epigaea  repens,  structure  of,  163 
Epiphlceum,  25,  60 
Equipment  of  botanical  student,  18 
Equisetacese,  vasal  bundles  of,  457 
Erythronium    Americanum,    69,    181, 

185;  illustrations,  185 
Krythrophyll,  416 
Ether,  sulphuric,  as  reagent,  265 
Eucalyptus  globulus,  bifacial   leaf  of, 

503 

Eupatorium  purpnreum,  307 
Euphorbia  splendens,   laticiferous  tis- 
sue in,  387 

Evaporating-dishes,  256 
Evening  Primrose,  211 
Exorhizal  germination,  243 
Eye-pieces  of  microscope,  250,  252 
Eyes  of  potato,  their  nature,  57 


FAGUS  FERRUGINEA,  39,  83,  87,  89 

leaf  of  (illustration),  87 
Fagopyrum  esculentum,  175 
False  Solomon's  Seal,  45,  449,  491 
concentric  bundles  of,  449 
stem  ef,  491 
Fats,  blue  stain  for,  275 

ether  in  the  study  of,  265 

red  stain  for,  275 

tests  for,  19,  265,  275 
Fehling's  solution  as  reagent,  266,  425 
Fern,  Maidenhair,  89 

Koyal,  89 

Shield,  89 

stem-bundles  of,  451 

type  of  stem,  491,  492 
Ferns,  venation  of  leaves  in,  90 
Ferric  chloride  as  reagent,  19 
Ferric-alum  solution  as  test  for  tannins, 

433 
Ficus  Carica,  223,  387 

elastica,  504,  511 

leaf-section  (illustration),  511 
Field  Mustard,  137 

Fig,   fruit  of,    223,    227;    illustration, 
227 

laticiferous  tissue  in,  387 
Firs,  secretion-reservoirs  in,  439 
Fixation  by  acetic  acid  and  alcohol,  260 

by  picric  solutions,  261 
Flax  Plant,  117;  illustration,  123 

fibres,  369,  370 

flower  of,  117 

perennial,  117 

Floral  symmetry  of  Arabis,  138 
Flower,  cruciferous,  study  of,  137,  141 

dimerous,  study  of,  131,  135 

ericaceous,  study  of,  163,  167 

gynandrous,  of  Cypripedium,  191 

liliaceous,  181,  183,  185 

monochlamydeous,  study  of,  175,  179 

monocotyl  type  of,  181,  183, 185, 187, 
193,  195,  197,201 

of  aberrant  monocotyl,  197,  201 

of  Composite,  study  of,  169,  173 

of  Crticiferse,  137 

of  Cypripedium  acaule,  190,  195 

of  ericaceous  plant,  163,  167 

of  gamopetalous  dicotyl,  157, 161 

of  Narcissus,  187,  193 

of  ranunculaceous  plant,  125,  129 

papilionaceous,  study  of,  149,  155 

pistillate,  198 

rosaceous,  study  of,  143, 147 

staminate,  198 

typical,  of  dicotyl,  117,  123 
Flowering  Dogwood,  bark  of,  313 
Flowers,  colors  of,  415 

of  Indian  Turnip,  198 


528 


INDEX. 


Focusing  microscope,  278,  284 

Foliole  or  foliolum,  103 

Forms   for  description,    following    29, 

74,  116,  202,  228,  240 
Four  o'clock,  175 

Fragaria  Virginiana,  101,  143,  223 
Fragrant  Orchis,  187 
Fraxinus  Americana,  31,  39 
Fringed  Gentian,  157 
Fruit,  definition  of,  203 

of  Cherry.  205,  209 

ofColchicum,  211,  213,  215 

of  Coriander,  217 

of  Fig,  223,  224 

of  Henbane  (Hyoscyamusniger),  214, 
215 

of  Lemon,  217,  219 

of  Pea,  204,  209 

of  Poppy,  211,  215 

of  Wintergreen,  223 
Fruits,  accessory,  223,  227 

aggregated,  204 

apocarpous,  203,  209 

illustrations  of,  209,  215,  221,  227 

multiple,  204 

ofUmbellifera,  217,  221 

superior,  204 

syncarpous,  211,  215,  217,  221 
Fuchsin,  acid,  in  study  of  amyloplasts, 

etc.,  400 
of  crystalloids,  409 

solution,  uses  of,  273,  400,  409 
Fumariacese,  flowers  of,  119 
Funaria  hygrometrica,  89 
Fungi,  callose  in,  382 

crystalloids  in,  410 
Fungus  cellulose  as  affected  by  chromic 

acid,  260 
Furcate  venation,  90 

GALANTHUS  NIVALIS,  69 
Gamopetalous  corolla,  157 
Gamosepalous  calyx,  143 
Garlic,  69 

(Janltheria  procumbens,  163,  223 
Gentiana  alba,  epidermis  of,  319 

crinita,  157 

Gentian-violet  solution,  273 
Geranium,  Horseshoe,  corky  tissue  of, 

335.  343 

epidermal  Appendages  of,  327,  333 
maeiilatum,  4o,  101,  117,  211,  430 
(Pelargonium)  leaf  of,  76,  81 
(Pelargonium)  stem,  ducts,  ami  tra- 

dieids  of,  351,  355 
(Pelargonium)    stem,  libriform    tis- 
sues of,  346,  349 
tissues  ,,f.  -J'.i2,  297 
<  ierminatiou,  i-mlorhi/al,  243 


Germination,  exorhizal,  243 
Ginger,  resin-sacs  in,  429 
Gink  ho  Tree,  leaves  of,  89,  95 
Glabrous  leaf,  78 

Gladiolus  communis,  65,  67 ;  illustra- 
tion, 67 
corm  of,  65,  67 
psittacinus,  65 
Glandular  hairs  of  Pelargonium  zonale, 

327,  333 

Glandular-pubescent  leaf,  78 
Glaucium  luteum,  hairs  of,  331 
Glaucous  leaf,  78 
Gleditschia  triacanthos,  335 
Globoids  in  aleurone-grains  of  Castor 

Bean,  408 
Glycerin   as    mounting    medium    and 

reagent,  265 

gelatin,  process  of  mounting  in,  275 
Glycyrrhiza  glabra,  491 
Golden  Club,  197 
Gold-size  in  mounting,  277 
Goldthread,  apocarpous  fruits  of,  203 

flower  of,  125,,  129 
Gooseberry,  211 

Gram's  method  of  staining,  274 
Grape,  collenchyma  in  petiole  of,  307 
sieve-tissue  of,  379 
Summer,  leaves  of,  101 
Green  Dragon,  65,  197 

mucilage-  and  crystal-sacs  in,  430 
section  of  stem  showing  crystal-sacs 

(illustration),  437 
Greenbriar,  31,  107 

closed  collateral  bundles  of,  457 
stem  of,  491 

Grenadier's  alum  carmine,  271 
as  nuclear  stain,  287 
use  of,  478 

hfematoxylin  solution,  271 
Ground  Cherry,  157,  211 

plans  of  flowers,  123,  129,  133,  135, 
141,  147,  155,  161,  167,  179,  185, 
192,  193,  195 
Ground-nut,  57 

Guard-cells  of  stomata  in  Tulip  leaf,  320 
Gymnospermsp,  244 
Gymnosperms  and  dicotyls,  secondary 

changes  in  roots  of,  481 
leaf-venation  of,  90,  92 
trwheids  of,  359 
Gynoscium,  118, 144, 158, 165, 176, 182, 

189,  192 

of  Cypripi'ilium,  192 
ol  KYythronium,  182 
of  Narcissus,  189 

HABENARIA  CILJARIS,  187 
leucophaea,  187 


INDEX. 


529 


Hair  of  Tradescantia  Virginica,  330 ; 

illustration,  333 

Hairs  of  Pelargonium  zonale,  327 ;  il- 
lustration, 333 

uses  of,  33 

Hamamelis  Virginica,  491 
Hardening  of  soft  tissues,  20,  264 

bv  potassium  bichromate,  268 
Harebell,  157 
Hazel-nut,  313 
Head,  138 

Heath  family,  stamens  of,  164 
Hedera  helix,  23,  89 

leaf  of  (illustration),  97 
leaf-venation  of,  93 
Hedge  Bindweed,  157 
Helenium  autumnale,  169 
Helianthus  annuus,  31,  169 

tuberosus,  57,  169 
Hellebore,  181 
Hemp  fibres,  369 

Henbane,  fruit  of,  211 ;  illustration,  215 
Heracleum  lanatum,  439 
Herbaceous  leaf,  79        * 
Hesperidia,  218 
Hesperis  matronalis,  137 
Hibiscus  Syriacus,  211,  416,  417 
Hickory,  epidermal  appendages  of,  327 

nut,  313 

stem,  31,  40,  49,  51 ;  illustration,  37 
Hieracium  venosum,  169 
Hilum-scar,  230 
Histology,  vegetable,  249 
Holchus  saccharatus,  424 
Honey  Locust,  cork-tissue  of,  335 
Hop  tree,  root-bark  of,  313 

sieve-tissue  of,  379 
Hordeum  distichon,  241 
Horse-chestnut,  31 
Horse-radish,  137 
Horseshoe  Geranium,    tannin-sacs   in, 

430 
Houstonia  cserulea,    157 ;    illustration, 

161 

Humulus  Lupulus,  379 
Hyacinth  bulb,  283 

centric  leaf  of,  504 

epidermis  of,  319 

leaves,  chlorophyll  in,  414 

Wild,  69 

Hyacinth  us  oriental  is,  69,  504 
Hydrogen  peroxide  as  bleaching  agent, 

261 

Hyoscyamus  niger,  calyx  of  (illustra- 
tion), 215 
fruit  of,  211,  214 
Hypocotyl,  243 
Hypocrateriform  corolla,  162 

perianth,  187 

34 


Hypoderma,  492,  507,  509 

of  leaf  of  Australian  Pine,  509 

of  Cycas  revoluta,  507 
Hypogynous  flower,  133 

IMPATIENS  FULVA,  211 
Indefinite  stamens,  126,  144    - 
Indeterminate  anthotaxy,  137 
Indian  Corn,  341 
stem  of,  491 
Cucumber,  57,  181 
Turnip,  65,  197 
air-spaces  in,  439 
leaf- venation  of,  92 
radial  bundle  in  root  of,  467 
roots  of,  477 
stem  of,  491 

Innate  anthers,  127,  139 
Introrse  anthers,  139 
Inula  Helenium,  423 
Inulin,  crystallization  of,  265 

crystals    in    Chicory   root   (illustra- 
tion), 427 

dissolved  by  sulphuric  acid,  259 
recognition  of,  263 
study  of,  423 

takes  place  of  starch  in  Compositse,  27 
Involucre  in  Compositse,  169 
Iodine,  chloral-hydrate,  as  reagent,  264 
chloriodide-of-zinc,  as  reagent,  263 
potassium-iodide,  as  reagent,  19,  263 
Iodine-green   in   study  of  laticiferous 

tissues,  388,  389 
solution,  272 

use  as  a  stain,  358 
Ipomeea  purpurea,  157,  235 
Iridacese,  65 

Iris  versicolor,  45,  83,  211,  448,  477 
Isolation  of  fibrous  tissues,  347 
Ivy,  crystalloids  in,  410 
English,  23,  89 
leaf-venation  of,  93;  illustration,  97 

JAMESTOWN  WEED,  157 
Japanese  filter-paper,  279 
Javelle  water  as  reagent,  267 
Jerusalem  Artichoke,  57,  169 
Jewel  Weed,  211 
Joe-Pve  Weed,  307 
Jonquil,  187 

Jubula  Hutchinsise,  89,  283 
Juga  of  umbelliferous  fruits,  217 
Juglans  cinerea,  358 

nigra,  358 
Jungermannia  barbata,  89 

Schraderi,  89,  283 

KALMIA  LATIFOLIA,  163 
Knife  for  sectioning,  255 


530 


INDEX. 


LABARRAQUE'S  SOLUTION  as  reagent, 

267,  313,  468,  509 
Lactuca  Canadensis,  387 

Scariola,  387 
Lady's  Slipper,  radial  bundle  in  root 

of,  467 
roots  of,  477 

Showy,  centric  leaf  of,  504 
Stemless,  187,  190,  195 
Lamina  of  leaf,  76,  78 
Lamination  in  starch-grains,  266 
Lanuginous  leaf-surface,  78 
Larch,  European,  bast-fibres  of,  369 
Large-flowered  Trillium,  181 
Larix  Americana,  367,  492 
Europsea,  367,  375 

bast-fibres  of  (illustration),  375 
Larkspur,  120,  125 
Lateral  anthers,  127 
Latex  of  Milkweed,   composition   of, 

389,  390 

Lathyrus  aphaca,  107 
maritimus,  107 

odoratus,  149 ;  illustration,  155 
palustris,  149 

Laticiferous  tissue,  complex,  389 
different  kinds,  390 
of  Asclepias  cornuti  (illustration), 

393 
simple,  388 

of  Dandelion  (illustration),  395 
study  of,  387 

Leaf,  basi-nerved,  91,  97,  99 
bifacial,  503 
branching  of,  101 
centric,  503;  illustration,  519 
costate-reticulate,  93 
foliage,  75 
unpaid-pinnate,  103 
incised,  102,  103 
of  I'arU'iTv,  75 
of  I'.eech  (Fagus),  83,  87 
of  Kloodroot,  131 
of  Cactus,  7"> 

of  Clover  (Trifoliurn),  84,  87 
of  Diomea,  75 
of  Fagus  ferruginea,  83,  87 
of  (  u-raniiun,  76 
of  Moss,  89 
of  I 'ra.  7") 

of  Sarraccnia,  7">,  107 
of  Tri folium  pratense,  84,  87 
of  I  'tricularia,  7-~> 
of  Vetch.  7-") 
palmately  compound,  104,  105 

palmi-nerved,  92 
palmi-reticulate,  •'••.  -'7 
pinnately  compound,  103,  105 
pinni-nerved,  '•'- 


Leaf,  pinni-reticulate,  93,  99 
prefoliation  of,  83,  87     • 
rib-netted,  93 
runcinate,  102,  105 
serrately-toothed,  103 
structure,  study  of,  503 
surfaces  of,  77 
uses  of,  75 

venation  of,  90,  95,  97,  99 ;  illustra- 
tions, 95,  97,  99 
Leaf-scars,  41,  58 

Leather  Leaf(  Cassandra  calyculata), 163 
Leaves,  bifacial,  504 

specially-modified,  107 
Legume,  205 
Lemna  polyrrhiza,  23 
Lemon,  2li,  217,  221,  243 
embryo  of,  243 

fruit  of,  217  ;  illustration,  221 
Lenses,  mode  of  cleaning,  21 
Lenticels,  32,  335,  338,  339,  341 
formation  of,  338 
function  of,  339 
of  Platanus  occidentals  (illustration), 

341 

study  of,  335 
Leucoplasts  in  hairs  of  Pelargonium 

zonale,  328 

Leucothoe  racemosa,  163 
Liber-fibres,  study  of,  367 
Libriform  cells,  study  of,  345 
Licorice,  rhizome  of,  491 
Lignified   membranes,   recognition   of, 

20,  262,  270,  272,  273 
tissues,  phenol  and  HC1  reagent  for, 

262 

staining  of,  272,  273 
test  for,  20 
Lilac,  31  n 

Liliaceous  flower,  1^1 
Lilium  Canadense,  69,  491 
candidurn,  69 

bulb  of  (illustration),  73 
Japonicum,  69 
Philadelphicum,  69,  181 
superbum,  1*1 
tigrinmn,  <i<),  181,  491 
Lily,  Atamasco,  (i'.t 
bulb,  <;<>,  283 
(alia,  197 

( 'aiiaila  or  Yellow,  69 
of  the  Valley,  -15,  89 
Tiger,  89,  7<>.  1M 
White  Japan,  69 
Wild  Oranue-red,  69 
Wild  Yellow,  stem  of,  491 
Liinnantheinuin,  trichoblasts  in,  440  ^ 
Linaria    vuliraris,    coloring   matter    in 
(lowers  of,  416 


INDEX. 


531 


Linen  fibres,  118 
Linum  perenne,  117 

usitatissimurn,  117,  123 

flower  of,  117  ;  illustration,  123 
Liriodendron  tulipifera,  83 
Live-for-ever,  117 

epidermis  of,  319 
Liverwort,  leaf  of,  89,  90 
Lizard's  Tail,  air-spaces  in,  439 
open  collateral  bundles  of,  457 
resin-sacs  in,  429 
stem  of,  491 
Locust,  corky  tissue  of,  335 

crystals  in,  434 

leaf  of,  101,  107 
Lungwort,  157 
Lupine,  flower  of,  149 

leaf  of,  103 ;  illustration,  105 
Lupinus  perennis,  149 

varius,  407 

Lychnis  Githago,  211 
Lycopodium  clavatum,  491 

inundaturn,  491 

obscurum,  491 

stem  of  (illustration),  499 

Selago,  491 
Lysigenous  intercellular  spaces,  440 

reservoirs,  development  of,  442 

MADEIRA  VINE  (Boussingaultia),  57 
Magnifying-power,      how      estimated, 

253 
Magnolia  glauca,  301,  429 

bark  of,  313 
grandiflora,  301 
Umbrella,  367 
bark  of,  313 
Maidenhair  Fern,  89 
Maize  (Indian  Corn),  23,  31,  247,  341, 

424,  467,  477,  491,  501 
grain  of  (illustrations),  247 
radial  bundle  in  root  of,  467 
roots  of,  477 

stem  of  (illustration),  501 
sugar  in.  424 
Male  Fern,  bifacial  leaf  of,  503 

concentric  bundles  of,  448 
Mallow,  89 

Malva  rotundifolia,  89 
Maple,  Red,  32 
Silver,  31,  229 
Sugar,  89 

Maples,  pitted  ducts  in,  358 
Marchantia    polymorpha,  chloroplasts 

of,  413" 

Marginal  Shield-fern,  concentric  bun- 
dles of,  448 

Marsh  Marigold,  125,  203 
Vetchling,  149 


Marshmallow  root,  mucilage  sacs  in, 

429 

section  of  (illustration),  435 
Mayapple  (Podophyllum),  45,  51,  53, 

379,  467,  471 

radial  bundle  in  root  of,  467 
rhizome  of,  45 
sieve-tissues  of,  379 
Meadow  Rue,  101 
Medeola  Virginiana,  57,  181 
I  Meditullium,  25,  26 
Medulla,  or  pith,  496 
Medullary  rays,  360,  496 

appearance  of,  in  different  sections, 

360 

Membranes,  thin,  study  of,  269 
Membranous  leaves,  79 
Menispermum  Canadense,  45,  203,  313, 

367,  457,  491,  495,  501 
stem  of,  495;  illustration,  501 
Mentha  Piperita,  45 
Mentzelia  oligosperma,  327 

ornata,  3:27 
Mercuric  chloride  as  reagent,  265,  400, 

409 
in  study  of  aleurone-grains,  409 

of  amyloplasts,  400 
Mericarp,  217 
Meristem  tissue,  459 
Mertensia  Virginica,  157 
Mesophloeum,  26,  60 
Mesophyll,  77,  508  ^ 
Methyl-green  as  stain,  272 

in  study  of  cork,  337 
Mezereum,  bast-fibres  of,  367,  370 
Micrometer,  stage,  254,  255 
Micropyle-scar,  238 
Micro-reagents,  258 
Microscope,  compound,  249,  251,  252 ; 

illustration,  251 
dissecting,  18;  illustration,  23 
optical  parts,  252 
parts  and  construction  of,  249 
stand,  249-251 
Microscopic  work,   general   directions 

for,  278 

Microsomes,  300 
Microtome,  257 

Middle  lamella,  nitric  acid  and   am- 
monia test  for,  260 
Milk-vessels  of  Dandelion,  26 
Milkweed,  203 

flowers  of,  120 
Millon's  reagent,  265 
Mirabilis  Jalapa,  175 
Mitchella  repens,  157 
Mnium  cuspidatum,  283 

serrntum,  89 
Monkshood,  57,  125,  477 


532 


INDEX. 


Monkshood,  roots  of,  477 
Monochlamydeous  flower,  176 
Monocotyl,  aberrant,  1U7.  199 

and  dicotyl  steins,  differences,  50,  51 

flowers  of,  177 

stems,  bundles  of,  451 

type  of  stem,  491,  41  >  1 
Monocotyls,  leaf-venation  of,  92 

roots  <>f,  477 
MonoBcism    and    diceclsm    of    Indian 

Turnip,  198 
Moonseed,  2(»3 

Moonwort  Fern,  radial  bundle  in  root 
..!.  467 

•  Morning-glory,  120,  157,  235 

flowers  of,  120 
Morus  rubra,  223 
Moss,  chloroj (lasts  of,  413 

leaf  of,  89 ;  illustration,  97 
Mossy  Stonecrop,  117 
Mountain  Ash,  American,  101 

Laurel,  163 
Mounting  media,  275 

process  of,  276 
Mucilage-sacs,  429,  431 
Mulberry,  223 

Mullein,  epidermal  appendages  of,  327 
Multiple  fruits,  204 
MUSH  sapientum,  425 
Musk-melon,  sugar  in,  425 
Mustard,  Field,  137 

NAPHTHOL  (a]  and  sulphuric  acid  as 
sugar  test,  425 

as  reagent,  270,  425 
Narcissus,  epidermis  of.  319 

flower  of  (illustration),  193 

.lonquilla,  187 

poeticus,  187 
flowers  of,  187 

Pseudo-narcissus,  69,  187,  504 

Tazetta,  187 
Nasturtium  Armoracia,  137 

(Tropeolum)    coloring    matters    in 

ilowers  of,  416 
Needles,  dissecting,  255 
Nepenthes  ampullaria,  107 

Chelsoni,  leaf  of  ( illustration),  115 
N'crimn  <  Meander,  :\:\\  :;s7.  •")(>:; 
Nerved  or  parallel  venation,  Hi,  97,  99 
Netted  venation.  (.l'J.  (.»7,  99 
Nettle,  l.ifacial  leaf  of,  :.<»  i 

hairs,  327,  .'I.".! 
Nicotiana  Tabacum.  '.\'2~ 
Nitella.    protoplasmic    movements   in, 
331 

Nitrates,  diplienylaiiiin   as   reairent  for. 

267 

Nucleus,  carmine  >iain  lor.  '.!,  1 


Nucleus,  crystalloids  in,  410 
defined  by  acetic  acid,  260 
figures,  study  of,  261 
fixing  and  staining  of,  272 
Grenadier's  alum-carmine  stain  for, 
•Js7 

Numerical  plan  of  flowers,  119 
Nuphar  ad  vena,  83,  235,  431),  14:', 

sections  (illustrations),  443 
Nux  Vomica,  '2'.\~> 
Nymplnea  odorata,  439 

OAK,  OVERCUP.  229 
Oat,  embryo  of,  241 

starch  of,  400 

Objectives,  250,  251,  252,  253 
Obtuse  apex  of  leaf,  78 
Octonate  leaf,  104 
CEdogonium  princeps,  283 
CEnothera  biennis,  211 
Oil   in    endosperm    of    Castor    Bean, 

408 

Oleacese,  flowers  of,  119 
Oleander,  bifacial  leaf  of,  503 

cork-tissue  of,  335 

laticiferous  tissue  of,  387 
Onion  bulb,  scale  of,  283 

epidermal  cells  of  (illustration),  289 

radial  bundle  in  root  of,  467 

Wild,  69 

Onoclea,  venation  of,  91 
Ophioglossum,  bundles  of,  457 
Opium  Poppy,  211,  387 

laticiferous  tissue  in,  387 
Opuntia  Rafinesquii,  107 
Orange,  211,  229,  439,  442 

secret!  on -reservoirs  in,  439,  442 
Orbicular  leaf,  78 
Orchis,  187 

mascula,  430 

mucilage- and  crystal-sacs  in,  430 

spectabilis,  1*7 
Organography,  16 
Qrnithogalum  umbellatum,  181 
( )rontium  aqiiaticutn,  177 
Orthostachies,  40 
Osmorrhiza  longistylis,  235 
Osmunda,  vasal  bundles  of,  4">7 

re-alis.  83,  89,  00,  ^ 

leaflet  of  (illustration),  95 
venation  of,  90 
Ovary  of  (  ypripedium,  192 

of  Flax,  ns 
Overcup  Oak,  22!) 
Oxalis  Acetocella,  117 

corniculata.  1 17 

viohicea.  till 
Ox-eve   I)ai>y.   H',9,   17:'. 

Bower-head  of  (illustration),  173 


INDEX. 


533 


PACKING-CELLS,  339 
Pale  Corydalis,  131 
Palisade  cells,  Cycas  revoluta  (illustra- 
tion), 515 
parenchyma,  503 
tissue  of  Cycas  leaf,  507 
Palm,  Cocoanut,  244 
Palmetto,  89 
Sabal,  89 

Palmi-reticulate  leaf,  93,  97 
Pancratium  maritimum,  187 
Papaver  somniferum,  131,  211,  387 
Papaveracere,  flowers  of,  119 
Papilionaceous  flower,  149 
Pappus  of  Composite,  170 
Parallel  venation,  91,  97,  99 
Parenchyma,    folded,    of    Pine     leaf, 

509 

of  Pumpkin  stem  (illustration),  303 
pitted,  301 

of    Cycas   revoluta    (illustration), 

305 

of  leaf  of  Austrian  Pine,  509 
spongy,  505 
study  of,  299 
tissue,  unequal   thickening  in  walls 

of,  300 

Parilla,  Yellow,  bast-fibres  of,  367 
Parsnip,  air-spaces  in  stem  of,  439 

stem  of,  491 
Partridge-berry,  157 
Pastinaca  sativa,  439,  491 
Pea,  73,  203,  204,  207,  209,  229 
fruit  of,  203,  204;  illustration,  209 
leaves  of,  73 
seed  of,  207 

Peach,  144,  203,  229,  425 
flower  of,  144 
sugar  in,  425 
Pear,  211,  313,  425 
flesh  of,  313 
sugar  in,  425 
Pecan,  313 

Pelargonium  zonale  (Horseshoe  Gera- 
nium), 81,  292,  297, 327, 333, 335, 
343,  346,'  349,  351,  355;  430 
cork-formation    in     (illustration), 

343 

ducts  of  (illustration),  355 
hairs  of  (illustration),  333 
leaf  of  (illustration),  81 
stem,  tissues  of,  292,  297 
tannin-sacs  in,  432 
tracheary  tissues  in,  351 
wood-fibres  of,    346 ;    illustration, 

349 
Pellitory,  inulin  in  root  of,  423 

secretion-reservoirs  in,  439 
Peltandra  Virginica,  197 


Pencils  for  drawing,  276 
Peppermint,  45 
Perennial  Flax,  117 
Perianth  of  Erythronium,  182 

of  Narcissus,  187 
Periblem,  478 
Pericambium,  468 
Pericarp  of  Cherry,  205 
Perisperm,  229,  230,  237 
Petals,  118,  126,  132,  138, 143, 150, 182, 
188,  190 

as  nectaries,  126 
Petiole,  76,  79,  103 
Phaseolus  multiflorus,  149.  203,  229 
Phellogen,  358 
Phenol  as  reagent,  262 
Phloem  of  vasal  bundles,  447 
Phloem-sheath,  468 
Phloroglucin  reagent,  uses  of,  20,  270, 
301,  315,  346,  379,  449,  457,  458, 
492,  493,  506 
Phlox  divaricata,  157 

flowers  of,  120 
Phrenix  dactyl ifera,  241 
Phyllodia,  108 
Phyllotaxy,  40,  59 

determination  of,  59 

of  potato,  59 

Physalis  pubescens,  157,  211 
Phytolacca  decandra,  175 
Pickerel-weed,  air-spaces  in,  439 

stem  of,  491 

Picric-nigrosin  solution,  274 
Pie-plant,  307 
Pilocarpus  Jaborandi,  301 

Selloanus,  301 
Pincettes,  255 

Pine,  secretion-reservoirs  in,  439 
Pineapple,  203,  223 
Pinguicula  vulgaris,  107 
Pinni-reticulate  leaf,  93,  99 
Pinons,  244 
Pinus  flexilis,  241 

Laricio,  504 

leaf  of,  508  ;  illustration,  519 

monophylla,  241,  244 

seed  of  (illustrations),  247 

ponderosa,  241 

Strobus,  491 

Torreyana,  241 
Pinxter-flower,  163 
Pipe  Vine,  flower  of,  175 

stem  of,  491 
Piper  nigrum,  235 
Pistil  of  Blood  root,  133 
Pistils,  118 

stipitate,  127 

Pisum  sativum,  203,  204,  229,  407 
fruit  of,  203,  204 


534 


INDEX. 


Pitcher-plant   (Sarracenia),    107,   108, 

109,  113 

(East  Indian)  (illustration),  115 
Pith,  34,  496 

use  of,  in  sectioning,  468 
Pits,  bordered,  of  gymnosperms,  360 

nature  of,  352 

Pitted  duct,  358;  illustration,  363 
Placentation  of  compound  pistil,  176 
Planta.iro  major,  89 
Plantain,  Common,  89 
Platanus  occidentalis,   327,   335,   341, 

491 

lenticel  of  (illustration),  341 
Plerome,  478 
Plum,  203,  229 

Podophyllum  peltatum  (May  apple), 
45,  53,  379,  467,  471 ;  illustra- 
tion, 53 

radial  bundle  in  root  of  (illustra- 
tion), 471 
rhizome  of,  45 
Poets'  Narcissus,  187 
Pogonia  ophioglossoides,  187 
Pokeweed,  175 
Polariscope,  257 

use  of,  in  study  of  starch,  379,  434 
Polarized   light   in  study  of  crystals, 

434 

Pollen,  118,  167 

Pollination  of  Cypripedium,  192 
Polyanthus,  187 
Polygonatum    biflorum,   45,   49,   491 ; 

illustration,  55 
giganteum,  89 
Polypodium    vulgare,    89,    101,    448, 

491 
Polypody    (Polypodium    vulgare),   89 

101 

concentric  bundles  of,  448 
Pomegranate  root-bark,  crystal-sacs  in, 

429 

Pondweed,  chloroplasts  of,  413 
Pontederia  cordata,  439,  491 
Poppy,  131 

capsule  (illustration),  215 
fruit  of,  211 
Opium,  211 

Populus  balsamifera,  31,  39,  335 
Pore-canals  in  bast-fibres,  368,370 

in  sclerotic  parenchyma,  315 
Potamogeton,  chloroplastB  of,  413 
Pota-Miini  bichromate  as  reagent,  267 
I'eiTocyanide  as  reagent,  2(>s 
hydrate  as  reagent,  !'.>,  202,  336 
in  study  of  chloroplasts,  415 
<»f  cork,  336 
of  crvMalloids,  401 

of  starch.  399 


Potassium-iodide  iodine  as  reagent,  263 
as  test  for  proteid,  285,  398 

for  starch,  397 
in  study  of  aleurone-grains,  408 

of  chloroplasts,  414 
Potato,  57,  63,  157,  211,  403 
berry,  211 
starch  of,  57 
tuber  (illustration),  63 

section  of  (illustration),  403 
Potentilla  anserina,  101 
Canadensis,  101,  143 
flower  of,  144,  145 
Pothos  pertusa,  roots  of,  477 
Prairie  Kose,  143 
Prefoliation,  83 
Preservation  of  tissues,  264 
Prickly  Pear,  107 

Poppy,  131 
Primary  root,  23 
Prince's  Pine,  163 
Proteids,    potassium-ferrocyanide    test 

for,  268 
recognition  of,   259,    260,  263,  265, 

266,  268 

staining  of,  266,  398,  400,  401 
Protein   crystals,  recognition   of,    263, 

400,  401 

Prothallia,  chloroplasts  in,  413 
Protoplasm,  carmine  stain  for,  271 
fixation  of,  by  chromic  acid,  260 
by  nitric  acid,  260 
by  osmic  acid,  261    . 
how  affected  by  sulphuric  acid,  258 
movements  of,  in  hairs  on  filament 

of  Tradescantia  Virginica,  330 
potassium-iodide  iodine  test  for,  263 
recognition  of,  261,  263 
study  of  continuity  of,  264 
sulphuric  acid   and   sugar   test   for, 

259 

xantho-proteid  test  for,  260 
Protoplasmic     movements    in     Nettle 

hairs,  Chara,  Nitella,  etc.,  331 
Primus  Americana,  143 
Amy^lalns,  229 
avium,  83,  143,  147,  203 
flowers  of,  143 

fruit  of,  203;  illustration,  147 
domestica,  203,  229 
persica,  203 

Ptelea  trifoliata,  root-bark  of,  313 
Pteris    aquilina,   357,    448,   449,   453, 

491,  499 
concentric  bundle  of  (illustration), 

-4-.:; 
Bcalariform  ducts  of,  357 

stem  of  (illustration),  499 
Pulvinns.  7!» 


INDEX. 


535 


Pumpkin,  229,  233,  299,  303,  358,  383, 
457,  491 

bi-collateral  bundles  in,  457 

dotted  ducts  in,  358 

seed  of  (illustration),  233 

seeds  of,  229 

sieve-tissue  of,  379 

stem  of,  491 

parenchyma  of,  299,  303 
section  of  (illustration),  383 
Punctuni  vegetationis  of  root,  479 
Punica  granatum,  429 
Purple    Milkweed,   laticiferous   tissue 
in,  387 

stonecrop,  117 
Putamen  of  Cherry,  205 
Pyrola  elliptica,  163 
Pyrus  Americana,  101 

communis,  211,  425 

coronaria,  211 

mains,  211,  229,  335,  425 
Pyxis  of  Hyoscyamus  niger,  214 

QUERCUS  ALBA,  101,  229 

macrocarpa,  229 

KACEME,  138 

Rachis  of  compound  leaf,  103 

Radial  bundle  in  root  of  Cypripedium 

spectabile,  469,  473,  475 
of  Podophyllum    (illustration), 

471 
bundles,  study  of,  467,  469,  471,  473, 

475 

Radish,  root  of,  23 
Ranunculaceous  flower,  1 25 
Ranunculus  bulbosus,  203 
repens,  467 

flower  of,  126 
septentrional  is,  125,  477 
Raphanus  Rhaphanistrum,  23 
Raphe,  229,  231,  235 
Raphides  in  Arissema  Dracontium,  432 
Rattlesnake  Weed,  169 
Ray-flowers  of  Composite,  170 
Rays,  medullary,  appearance  of,  in  dif- 
ferent sections,  360 
Reagent-bottles,  capped,  256 
Reagents,  care  of,  19,  21 
table  of,  following  281 
Red  Maple,  32 

Rose,  coloring  matter  in  flowers  of, 

416 

Reed  Bent-grass,  roots  of,  477 
Resin -sacs,  429,  430 
Resins,  red  stain  for,  20,  275 
Reticulate  ducts  and  tracheids,  352 

venation,  92 
Rhamnus  Purshiana,  429 


Rheum  officinale,  429 
Rhizome,  45,  49,  53,  55,  131,  175,  179 ; 
illustrations,  53,  55 

of  Bloodroot,  131 

of  Podophyllum,  48,  53 

of  Polygonatum,  49,  55 

of  Srnilacina,  concentric  bundle  of 
(illustration),  455 

of  Wild  Ginger  (Asarum  Canadense), 
175,  179 

study  of,  45 
Rhododendron  arborescens,  83 

nudiflorum,  163 
Rhubarb,  crystal-sacs  in,  429 
Ribes  cynosbati,  211 

nigrum,  335 
Rib-netted  leaf,  93 
Richardia  africana,  89,  197 
Ricinus  communis,  101,  235 
aleurone-grains  of,  407 
endosperm  of  (illustration),  411 
Rings  of  growth,  34,  497 
Robinia  Pseudacacia,  107,  149,  335 
Rock  Cress,  137 
Rocket,  137    , 
Rod-  or  staff-cells,  371 
Root,  how  distinguished  from  stem,  52, 
481 

regions  in,  478 

secondary  changes  in,  479 

section  of  Cimicifuga  (illustrations), 

485,  487,  489 

Root-branches,  origin  of,  469 
Root-cap,  28,  478 
Root-hairs,  24 
Root-tip  of  Calamagrostis  (illustration), 

Roots,  absorption  by,  24 

adventitious,  24 

bundles  in,  467 

of  dicotyls  and  gymnosperms,  26 

of  Podophyllum,  46 

study  of,  477 

table  for,  following  30 
Rosa  blanda,  101,  143 

canina,  143 

Carolina,  223 

Gallica,  416 

rubiginosa,  223 

setigera,  143,  223 
Rosacese,  flowers  of,  144 
Rose,  223 

Dog,  143 

flowers  of,  120 

leaf  of,  101 

smooth,  101 
Royal  Fern  (Osmunda  regalis),  83,  89, 

90,95 
Rubber  tree,  bifacial  leaf  of,  504 


536 


INDEX. 


Rubiacea?,  119,  157 

flowers  of,  119 
Rubus  CanadeoBU,  143 

villosus,  143 
Rudimentary  organs,  significance  of,  58, 

191 
Rue,  leaf  of,  101,  503 

Meadow,  leaf  of,  101 
Ruler,  graduated,  2-V> 
Rumex  crispus,  branch  of  (illustration), 

87 

crystal-sacs  in,  429 
prefoliation  of,  83,  84 
root  of,  23,  313 
seeds  of,  235 
obtusifolius,  358 
Russow's  potassium  hydrate  as  test  for 

resin,  430 
Ruta  graveolens,  leaf  of,  101,  503 

SABAL  PALMETTO,  89 

Saccharum  officinarurn,  424 

Safranin  solution,  273 

Sagittaria  variabilis,  439,  457 

Sago  Palm  (Cycas),  bifacial  leaf  of,  503 

pitted  parenchyma  of,  301 
St.  James'  Lily,  69 
Salisburia  adiantifolia,  89 
Salix  alba,  335 
Salsify,  inulin  in,  423 
laticiferous  tissue  in,  387 
root  of,  23 
Sambucus    Canadensis,   bast-fibres    of, 

367 

cork  and  lenticels  of,  335 
Sanguinaria  Canadensis,  flower  of,  131 

secretion-sacs  in,  429 
Sarcocarp  of  Cherry,  205 
Sarracenia,  leaves  of,  75,  107,  113 
flava,  leaf  of,  107 
purpurea,  leaf  of,  107 ;  illustration, 

113 
Sarsaparilla,  radial  bundle  in  root  of, 

it;: 

n.«.ts  of,  357,400,  467,  477 
scalariforrn  ducts  of,  357 
starch  of,  400 

Wild,  secretion-reservoirs  of,  439 
Saunirus  ceriums.   429,  439,  457,  458, 

463,  I'.'l 

open    collateral    bundles    of,    457, 
r.s;  Illustration,  463 

Scabrous  Ira!'.  7S 

Scalarilonn  duct,  353,  357,363;  illus- 
tration, :ji;:; 

of  Pelargonium  /.onale,  353 
Scaly  bulb,  (><) 

Scape  of  III In.ot,  132 

Scarious  leaf,  i  Jl 


Scarlet  Runner,  149,  203,  229 
Scars  on  seeds,  229,  230 
Schizogenous  intercellular  spaces,  440 

reservoirs,  development  of,  442 
Schulze's  maceration  fluid  in  study  of 

cork,  337 

uses  of,  316,  337,  347,  369 
Scilla  maritima,  429 
Scirpus  lacustris,  439,  457 
Scissors  for  dissecting,  255 
Sclerenchynui-fibres,  345,  370 
Sclerotic     parenchyma    of    Cocoanut 

(illustration),  317 
relation     to     sclerenchyma-fibres, 

345 

study  of,  313 

Scorzonera  hispanica,  387 
Scutellum,  242 

Secretion-reservoirs,  study  of,  439 
Secretion-sacs  containing  crystals  and 
mucilage,  429 

how  related  to  laticiferous  tissue,  390 

study  of,  429 
Section  knife,  253 
Sectioning,  20,  280,  321,  478 

leaves,  321 

thin  roots,  428 
Sedum  acre,  117 

flower  of,  119 

pulchellum,  117 

Telephium,  117 

epidermis  of,  319 
Seed,  albuminous,  230,  235,  239 

amphitropous,  230 

anatropous,  230 

atropous,  230 

campylotropous,  230 

exalbuminous,  230 

of  Almond,  229,  230,  233 

of  Black  Pepper,  235,  239 

of  Castor  Bean,  235,  239 

of  Cherry,  207,  2W 

of  Indian  Corn,  241,  247 

of  Lemon,  219,  221 

of  Pea,  207,  209 

of  Pinus  monophylla,  244,  247 

of  Pumpkin,  229,  231,  2.",:; 
Selaginella,  concentric  bundles  of,  448 

rupestris,  448 
Sela.^inelhe,  steins  of,  493 
Sensitiveness  of  Sundew,  111 
Sepals,    11 S.    121>,    1:12,    i:J5,    138,    143, 

id:;.  I'.io 

of  ( 'ypripedium,  1(.'<> 
Septicidal  dehisceiiee.  212 
Service-  1  Jerry,  21  1 

Sbeplicrdia  Canadensis,  bairs  of,  327 
Shepherd's  Purse,  101 
Shield  Fern,  SI'.,  S'j 


INDEX. 


537 


Shin-leaf,  163 

Showy   Lady's   Slipper  (Cypripedinm 
spectabile),  187,  467,  473,  475 
radial  bundle  of,  467 
Shrubby  Mallow,  211 

coloring  matters  in  flowers  of,  416 
Sieve-tissue,  function  of,  381 

of  Pumpkin  stem  (illustration),  383, 

385 

study  of,  379 
Silphium    laciniatum,    358,   367,   373, 

439 

bast-fibres  of  (illustration),  373 
Silver  Maple,  101,  103,  105,  229,  471 
leaf  of,  103;  illustration,  105 
stem  of,  491 

nitrate  as  reagent,  268,  400 
Weed,  101 
Skunk  Cabbage,  197,  467 

radial  bundles  in  root  of,  467 
Slides   for   mounting   microscopic  ob- 
jects, 256 

Slippery  Elm,  crystals  in,  433 
mucilage-sacs  in,  429 
sieve-tissues  of,  379 
Smilacina  racernosa,  45,  449,  450,  491 

concentric  bundles  in  stem  of,  450 
Smilax  officinalis,  467,  477 

rotundifolia,  23,   31,  107,  357,  457, 

491 

scalariform  ducts  of,  357 
Smooth  Rose,  101,  143 
Snapdragon   (Linaria  vulgaris),  color- 
ing matter  in  flowers  of,  416,  421 
Sneeze- weed,  169 
Snowdrop,  69 
Soda,  chlorinated,  265 
Soda-corallin    in   study   of   mucilage- 
sacs,  432 

Sodium  phosphate  as  reagent,  269 
Soft  bast  of  Pumpkin  stem  (illustra- 
tion), 383,  385 
Softening   hard   tissues,  20,   261,   263, 

266 

Solanacere,  dangerous  properties  of,  61 
Solanum  Dulcamara,  335,  457 

cork-formation     in     (illustration), 

343 

tuberosurn,  57,  157,  211,  403;  illus- 
tration, 63 
Solomon's  Seal,  45,  49,  89 

stem  of,  491 
Sonchus  oleraceus,  423 
Sorghum,  sugar  in.  424 
Sow-thistle,  inulin  in.  423 
Spadix,  138 

of  Indian  Turnip,  198 
Spanish  Salsify,  387 
Sparganium  eurycarpum,  439 


Spathe,  138 

Spider  wort,  closed  collateral  bundles 
of,  457 

coloring  matter  in  flowers  of,  416 

hairs  on  filament  of,  327 

mucilage-  and  crystal-sacs  in,  429 

stem  of,  491 
Spike,  138 

Spikenard,  secretion -reservoirs  in,  439 
Spinose  leaf,  78 

Spiral  ducts  of  Pelargonium,  353 
Spirogyra,  chloroplasts  of,  413 

crassa,  283 

Spongy  parenchyma,  504 
Spring  Beauty,  57 

Cress,  157 
Squash,  bi-collateral  bundles  of,  457 

sieve-tissue  of,  379 
Squill,  mucilage-  and  crystal-sacs  in, 

429 

Stachys  tuberifera,  57 
Staff-  or  rod-cells,  371 
Stage  micrometer,  253,  255 
Stagger-bush,  163 
Staining  fluids,  270 

Stamens,  118,  120,  126,  133,  139,  144, 
151,  158,  164,  171,  176,  182, 189, 
191 

diadelphous,  151 

gynandrous,  of  Cypripedium,  191 

indefinite,  126 

of  Bloodroot,  133 
Staminodes  of  Flax,  118,  123 
Star  of  Bethlehem,  181 
Starch  dissolved  by  sulphuric  acid,  258 

in  chloroplasts,  recognition  of,  415 
of  Moss  leaf  (illustration),  419, 
421 

in   Colchicum    autumnale    (illustra- 
tion), 405 

of  potato,  60  ;  illustration,  405 

red  stain  for,  274 

study  of,  262,  397 

test  for,  19,  263,  264 
Stavesacre,  235 

Stemless  Lady's  Slipper,  187,  211 
Sterns,  different  types  of,  491 

internal  structure  of,  33 

of  gymnosperms,  497 

study  of,  31,  491 
Stigma,  118,  147 
Stipules,  76,  79 
Stomata,  77 

arrangement  of,  in  different  leaves, 
323 

number  to  sq.  cm.,  323 

of  Cycas  leaf,  507 

of  Tulip  leaf,  320 

opening  and  closing  of,  322 


538 


INDEX. 


Stomrxtn,  structure  of  guard-cells  of,  320 
Stonecrop.  Mossy,  117 
Stony  tissue,  313 

Stramonium,  211 

Stratification,   demonstration    of,    268, 

399,  431 
in  mucilage,  -\'->\ 
in  starch-sprains,  399 
of  cell-wall,  208 
Strawberry,  101,  120, 143,  204,  223 

flowers  of,  120 
Strobile  -Jll 
Strophiole,  235 
Structural   characters,    importance   of, 

145 

Strychnos  Nux-vomica,  235 
Study  of  flowers,  form  for,  202 
..("Fruits,  form  for,  228 
of  Leaves,  form  for,  116 
of  Koots,  form  for,  30 
of  Seeds,  form  for,  240 
of  Stems,  form  for,  74 
Style,  118 
Stylopodia,  217 

Suberin  and  cutin,  nature  of,  336 
Suberized  tissues  as  affected  by  chromic 

acid,  260 

potassium-hydrate  reagent  for,  262 
study  of,  260,  262,  335  - 
succulent,  79 
Sugar  and  sulphuric  acid  as  test  for 

protoplasm,  259 
Maple,  89 

study  of,  266,  423,  424,  425 
test  for  (Fehling's),  266 
Sugar-beet,  sugar  in,  425 
Sugar-cane,  sugar  in,  424 
Sulphuric  ether  as  solvent,  263 
Sumach,  collenchyma  of,  307 

leaf-scars  of,  42 
Summer  <  I  rape.,  101 
Sundew,  Long-leaved,  107 
Kound-leaved,  107,110 
Sunflower,  31,  169 
Supernumerary  buds,  31 
Sweet  Hay,  bark  of,  313 

resin-sacs  in,  429 
Cicely,  '2:>-> 

Flag,  I-'.,  197,  429  430,  449,  467,  504 
centric  leaf  of.  odj 
concentric  bundles  of,  449 
radial  bundle  in  root  of,  467 
resin-sacs  in.   I'J'.i.  430 
roots  of.  177 

Tea  iLathyrus  odoratust,  149,  155 
Potato,  su-'ar  in.    \~~> 

Syca v.  -1-J.  :;-J7.  886,    I'.M 

c..rk\   ti>-ue  and  lenticels  of.  335 
epidermal  appendages  of,  .'127 


Sycamore,  leaf-scars  of,  42 

stem  of,  491 
Svconium,  225 

Symmetry,  floral,  118,  126,  183 
Symplocarpns  i'u'tidus,  467 
Syringa  vulgarls,  31 

TABLE  OF  REAGENTS,  following  page 

281 
Tamarack,  bast-fibres  of,  367 

stem  of,  492 
Tannin    and    osmic  acid   in   study   of 

crystalloids,  409 
bichromate  test  for,  267 
ferric  reagents  for,  266 
in  potato,  61 

potassium  hydrate  as  reagent  for.  2*'»:> 
recognition  of,  19,  20,  261,  263,  264, 

2<;r>,  2<57.  2f',S,  433 
Tannin-sacs,  430 
Tap-root,  24 
Taraxacum,  leaf  of,  101 

officinale,  23,  101,  169,  387,  423 
root  of,  23 

Tartarian  Honeysuckle,  32 
Taxodium  distichum,  359,  367,  492 

tracheids  of,  359 
Tea,  leaves  of,  313 
Tecoma  radicans,  101 
Tegmen  of  seed,  229 
Terminal  bud,  31,  38,  46,  50 
of  potato,  38 
structure  of,  46,  50 
Testa  of  seed,  229 
Tetradynamous  stamens,  139 
Thalictrum  dioicum,  101 
Thymol  and  sulphuric  acid  as  reagent 

for  inulin,  424 
for  sugar,  425 
with   hydrochloric   acid    as   reagent 

for  lignin,  270 
Tiger  Lily,  69,  70,  181,  I'.M 
Tilia  Americana,  31,  39,  101,  33-"..  :',ii7, 

379,  429,  457,  491 
Tissues  of    Pelargonium   /ouale   -tern 

(illustration ),  297 
of  the  higher  plants,  lM>l 
Toad-flax,   coloring   matter   in   flowers 

of,  416 

Tobacco,  epidermal  appendages  of,  :','J7 
Tooihwort.  :>7,  l:J7 
Trabecular  tracheids,  361 
Tracbeary   tissues,   study   of.   ."."'I.    355| 

857,  :'>M.  :;r>"> 
Traebeids,     how     distinguished     from 

ducts,  .">•">! 
of   Bald   Cypress,   8-V.) ;    illustration, 

365 
reticulate  (illustration),  355 


INDEX. 


539 


Tradescantia  Virginica,  319,  327,  333, 

416,  430,  457,  461,  491 
collateral  bundle  of  (illustration), 

461 

epidermis  of,  319 
hair  on  filament  of  (illustration), 

333 

Tragopogon  porrifolius,  23,  387,  423 
Trailing  Arbutus,  163 
Trichoblasts,  440,  443 
Trifolium  pratense,  83,  84,  87 
branch  of  (illustration),  87 
prefoliation  of,  84 
Trillium  erectum,  211 

grandiflorum,  181 
Triticum  vulgare,  241,  407,  504 
Tropeolum  majus,  416 
Trumpet  Creeper,  101,  102,  103,  105 

leaf  of,  102,  103;  illustration,  105 
Trumpet-plant,  107 
Tubers,  nature  of,  58 
Tulip,  211,  319 

epidermis  of  leaf  of,  319 
tree  (Liriodendron),  83 
Tulipa  Gesneriana,  211 
Tunicated  bulb,  70,  73 
Turk's-cap  Lily,  181 
Turn-table,  258 
Twigs,  comparison  of,  39 

ULMUS  FULVA,  367,  369,  429 
Umbel,  138 

Umbellifene,  fruits  of,  217 
Umbrella  tree,  bark  of,  313 

bast-fibres  of,  367 
Urtica  dioica,  327,  504 
Utricularia  vulgaris,  75,  107  • 
Uvularia  grandiflora,  89 
perfoliata,  181 

VACCINIUM  CORYMBOSUM,  163 
Vallisneria  spiral  is,  331,  413 
Vasal   bundles,   bi-collateral    (illustra- 
tion), 465 

closed  collateral  (illustration),  461 
in  fern  type  of  stem,  493 
in  Solomon's  Seal,  51 
kinds  of,  448 

open  collateral  (illustration),  463 
study  of,  447,  461,  463,  465,  492, 

493 

Venation,  90,  91,  92,  102 
furcate  type,  90 
nerved  type,  91 
relation  to  leaf-branching,  102 
reticulate  type,  92 
Venus'  Fly-trap,  107 
Venus-hair  Fern,  89 
Veratrum  viride,  181 


Verbascum  Thapsu^,  327 
Veronica  Virginica,  45,  467,  477 
Vetch,  leaves  of,  75 
Vetchling,  Marsh,  149 
Vexillary  aestivation,  150 
Vexillum,  150 

Viola  palmata,  var.  Cucullata,  83 
Violet,  83,  120,  211 

flowers  of,  120 

Wood-sorrel,  69 
Virgin's  Bower,  open  collateral  bundles 

of,  457 
stem  of,  491 
Vitis  sestivalis,  101 
Vittse,  217 
Volatile  oils,  test  for,  20,  275 

WALNUT,  BLACK,  229,  358 

English,  313 
Wandering  Jew,  89 
Watch-glasses,  256 
Water  Arum,  197 
Water  Lily,  83,  119,  439 
Water  Plantain,  241,  439,  457 
Water  Weed,  chloroplasts  of,  413 
Watermelon,  229,  379 
Wheat,  embryo  in  grain  of,  241 

leaf  of,  centric,  504 
White  Ash,  39 

Daisy,  169 

Japan  Lily,  69 

Lily,  69 

Oak,  101,  229 

Pine,  stem  of,  491 

Weed,  169 

Willow  (Salix  Alba),  cork-tissue  of, 

335 

Whorled  phyllotaxy,  40 
Wild    Cranesbill    (Geranium    macula- 
turn),  45,  101,  117,  211,430 

Ginger    (Asarum    Canadense),    175, 
179 

Hyacinth  (Camassia  Frazeri),  69,  181 

Lettuce,  Jaticiferous  tissue  in,  387 

Onion  (Allium  cernuum),  69,  181 

Orange- red  Lily,  69,  181 

Phlox  (Phlox  divaricata),  157 

Red  Plum,  143 

Yam,  89,  93 

leaf-venation  of,  93 

Yellow  or  Canada  Lily,  69 
Willows,  flowers  of,  119 
Wiutergreen,  163,  223,  227 

fruits  of,  223 

plant  of  (illustration),  227 
Witch  Hazel,  stem  of,  491 
Wood-cells     of     Pelargonium    zonale 

(illustration),  349 
study  of,  345 


540 


INDEX. 


Wood-parenchyma;  459 
Wood-sorrel,  117 
Woodwardia,  venation  of,  91 

XANTHO-PROTEID  REACTION,  258 
Xylem  of  vasal  bundles,  447 

YAM  FAMILY,  leaf-venation  of,  92,  93 

Wild,  89,  93 

Yellow  Adder's-tongue,  181 
Dock,  23,  83,  84,  235,  313,  429 
crystal-sacs  in,  429 
prefoliation  of,  84 
root-bark  of,  313 
Fringed  Orchis,  187 


Yellow  Lady's  Slipper,  187,  467 

Parilhi,  45,  457,  491 

Pond-lily,  235 

Vetdiling,  107 

Wood-sorrel,  117 
Yucca  filamentosa,  504 

ZEA  MAYS,  23,  31,  241,  424,  457,  467, 

477,  491 

Zinc-chloriodide  iodine  as  reagent,  263 
in  study  of  cork,  336 

of  mucilage-sacs,  431 
Zingiber  officinale,  4'29 
Zygnema,  chloroplasts  of,  413 
insigne,  283 


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One  of  the  most  attractive  features  of  the  book  is  its  illustrations.  Very 
many  of  them  are  original  and  faithful  reproductions  of  photographs  taken 
directly  from  patients  or  from  specimens,  and  the  modern  improvements  in  the 
art  of  engraving  have  enabled  the  publisher  to  produce  illustrations  which  it  is 
believed  are  superior  to  those  in  any  similar  work. 

CONTRIBUTORS : 


Dr.  Charles  H.  Burnett,  Philadelphia. 
Phineas  S.  Conner,  Cincinnati. 
Frederic  S.  Dennis,  New  York. 
William  W.  Keen,  Philadelphia. 
Charles  B.  Nancrede,  Ann  Arbor.  Mich. 
•  Roswell  Park,  Buffalo,  N.  Y. 
Lewis  S.  Pilcher,  New  York. 


Dr.  Nicholas  Senn,  Chicago. 

Francis  J.  Shepherd,  Montreal,  Canada. 

Lewis  A.  Stimson,  New  York. 

William  Thomson,  Philadelphia. 

J.  Collins  Warren,  Boston. 

J.  William  White,  Philadelphia. 


"  If  this  text-book  is  a  fair  reflex  of  the  present  position  of  American  surgery,  we  must 
admit  it  is  of  a  very  high  order  of  merit,  and  that  English  surgeons  will  have  to  look  very 
carefully  to  their  laurels  if  they  are  to  preserve  a  position  in  the  van  of  surgical  practice." — 
London  Lancet. 

"  The  soundness  of  the  teachings  contained  in  this  work  needs  no  stronger  guarantee  than 
is  afforded  by  the  names  of  its  authors." — Medical  News,  Philadelphia. 


W.   B.   SAUNDERS' 


For  Sale  by  Subscription. 


AN  AMERICAN  TEXT-BOOK  ON  THE  THEORY  AND 
PRACTICE  OF  MEDICINE.  By  American  Teachers.  Edited 
by  WILLIAM  PEPPER,  M.  D.,  LL.D.,  Provost  and  Professor  of  the  Theory 
and  Practice  of  Medicine  and  of  Clinical  Medicine  in  the  University  of 
Pennsylvania.  Complete  in  two  handsome  royal- octavo  volumes  of  about 
1000  pages  each,  with  illustrations  to  elucidate  the  text  wherever  necessary. 
Price  per  Volume  :  Cloth,  $5.00  net;  Sheep,  $6.00  net;  Half  Russia,  $7.00 

net. 

VOLUME  I.   CONTAINS: 


Hygiene. — Fevers  (Ephemeral,  Simple  Con- 
tinued, Typhus,  Typhoid,  Epidemic  Cerebro- 
spinal  Meningitis,  and  Relapsing). — Scarla- 
tina, Measles,  Rotheln,  Variola,  Varioloid, 
Vaccinia, Varicella,  Mumps, Whooping-cough, 
Anthrax,  Hydrophobia,  Trichinosis,  Actino- 


mycosis,  Glanders,  and  Tetanus. — Tubercu- 
losis, Scrofula,  Syphilis,  Diphtheria,  Erysipe- 
las, Malaria,  Cholera,  and  Yellow  Fever. — 
Nervous,  Muscular,  and  Mental  Diseases  etc. 


VOLUME   II.  CONTAINS: 


Urine  (Chemistry  and  Microscopy). — Kid- 
ney and  Lungs. — Air-passages  (Larynx  and 
Bronchi)  and  Pleura. — Pharynx,  (Esophagus, 
Stomach  and  Intestines  (including  Intestinal 
Parasites),  Heart,  Aorta,  Arteries  and  Veins. 


— Peritoneum,  Liver, and  Pancreas. — Diathet- 
ic  Diseases  (Rheumatism,  Rheumatoid  Ar- 
thritis, Gout,  Lithsemia,  and  Diabetes.) — 
Blood  and  Spleen. — Inflammation,  Embolism, 
Thrombosis,  Fever,  and  Bacteriology. 


The  articles  are  not  written  as  though  addressed  to  students  in  lectures,  but 
are  exhaustive  descriptions  of  diseases,  with  the  newest  facts  as  regards  Causa- 
tion, Symptomatology,  Diagnosis,  Prognosis,  and  Treatment,  including  a  large 
number  of  approved  formuloe.  The  recent  advances  made  in  the  study 
of  the  bacterial  origin  of  various  diseases  are  fully  described,  as  well  as  the 
bearing  of  the  knowledge  so  gained  upon  prevention  and  cure.  The  subjects 
of  Bacteriology  as  a  whole  and  of  Immunity  nre  fully  considered  in  a  separate 
section. 

Methods  of  diagnosis  are  given  the  most  minute  and  careful  attention,  thus 
enabling  the  reader  to  learn  the  very  latest  methods  of  investigation  without 
consulting  works  specially  devoted  to  the  subject. 


CONTRIBUTORS : 


Dr.  J.  S.  Billings,  Philadelphia. 
Francis  Delafield,  New  York. 
Reginald  H.  Fitz,  Boston. 
James  W.  Holland,  Philadelphia. 
Henry  M.  Lyman,  Chicago. 
William  Osier,  Baltimore. 


Dr.  William  Pepper,  Philadelphia. 
W.  Gilman  Thompson,  New  York. 
W.  H.  Welch,  Baltimore. 
James  T.  Whittaker,  Cincinnati. 
James  C.  Wilson,  Philadelphia. 
Horatio  C.  Wood,  Philadelphia. 


"  We  reviewed  the  first  volume  of  this  work,  and  said :  '  It  is  undoubtedly  one  of  the  best 
text-books  on  the  practice  of  medicine  which  we  possess.'  A  consideralion  of  the  second 
and  last  volume  leads  us  to  modify  that  verdict  and  to  say  that  the  completed  work  is,  in  our 
opinion,  THE  BEST  of  its  kind  it  has  ever  been  our  fortune  to  see.  It  is  complete,  thorough, 
accurate,  and  clear.  It  is  well  written,  well  arranged,  well  printed,  well  illustrated,  and  well 
bound.  It  is  a  model  of  what  the  modern  text-book  should  be."— New  York  Medical  Journal. 

"  A  library  upon  modern  medical  art.  The  work  must  promote  the  wider  diffusion  of 
sound  knowledge." — American  Lancet. 

"  A  trusty  counsellor  for  the  practitioner  or  senior  student,  on  which  he  may  implicitly 
rely." — Edinburgh  Medical  Journal. 


CATALOGUE    OF  MEDICAL    WORKS. 


For  Sale  by  Subscription. 


AN  AMERICAN  TEXT-BOOK  OF  THE  DISEASES  OF  CHIL- 
DREN. By  American  Teachers.  Edited  by  Louis  STARR,  M.  D., 
assisted  by  THOMPSON  S.  WESTCOTT,  M.  D.  In  one  handsome  royal-8vo 
volume  of  1190  pages,  profusely  illustrated  with  wood-cuts,  half-tone  and 
colored  plates.  Net  Prices  :  Cloth,  $7.00 ;  Sheep,  $8.00 ;  Half  Russia,  $9.00. 

The  plan  of  this  work  embraces  a  series  of  original  articles  written  by  some 
sixty  well-known  podiatrists,  representing  collectively  the  teachings  of  the  most 
prominent  medical  schools  and  colleges  of  America.  The  work  is  intended  to 
be  a  PRACTICAL  book,  suitable  for  constant  and  handy  reference  by  the  practi- 
tioner and  the  advanced  student. 

One  decided  innovation  is  the  large  number  of  authors,  nearly  every  article 
being  contributed  by  a  specialist  in  the  line  on  which  he  writes.  This,  while 
entailing  considerable  labor  upon  the  editors,  has  resulted  in  the  publication  of 
a  work  THOROUGHLY  NEW  AND  ABREAST  OF  THE  TIMES. 

Especial  attention  has  been  given  to  the  latest  accepted  teachings  upon  the 
etiology,  symptoms,  pathology,  diagnosis,  and  treatment  of  the  disorders  of  chil- 
dren, with  the  introduction  of  many  special  formulae  and  therapeutic  procedures. 

Special  chapters  embrace  at  unusual  length  the  Diseases  of  the  Eye,  Ear, 
Nose  and  Throat,  and  the  Skin ;  while  the  introductory  chapters  cover  fully  the 
important  subjects  of  Diet,  Hygiene,  Exercise,  Bathing,  and  the  Chemistry  of 
Food.  Tracheotomy,  Intubation,  Circumcision,  and  such  minor  surgical  pro- 
cedures coming  within  the  province  of  the  medical  practitioner  are  carefully 
considered. 

CONTRIBUTORS : 


Dr.  S.  S.  Adams,  Washington. 

John  Ashhtirst,  Jr.,  Philadelphia. 
A.  D.  Blackader,  Montreal,  Canada. 
Dillon  Brown,  New  York. 
Edward  M.  Buckingham,  Boston. 
Charles  W.  Burr,  Philadelphia. 
W.  E.  Casselberry,  Chicago. 
Henry  Dwight  Chapin,  New  York. 
W.  S.  Christopher,  Chicago. 
Archibald  Church,  Chicago. 
Floyd  M.  Crandall,  New  York. 
Andrew  F.  Currier,  New  York. 
Roland  G.  Curtin,  Philadelphia 
J.  M.  DaCosta,  Philadelphia. 
I.  N.  Danforth,  Chicago. 
Edward  P.  Davis,  Philadelphia. 
John  B.  Deaver,  Philadelphia. 
G.  E.  de  Schweinitz,  Philadelphia. 
John  Doming,  New  York. 
Charles  Warrington  Earle,  Chicago. 
Wm.  A.  Edwards,  San  Diego.  Cal. 
F.  Forchheimer,  Cincinnati. 
J.  Henry  Fruitnight,  New  York. 
Landon  Carter  Gray,  New  York. 
J.  P.  Crozer  Griffith,  Philadelphia. 
W.  A.  Hardaway.  St.  Louis. 
M.  P    Hatfield,  Chicago. 
Barton  Cooke  Hirst,  Philadelphia. 
H.  Illoway,  Cincinnati. 
Henry  Jackson,  Boston. 
Charles  G.  Jennings,  Detroit. 
Henry  Koplik,  New  York. 


Dr.  Thomas  S.  Latimer,  Baltimore. 
Albert  R.  Leeds,  Hoboken,  N.  J. 
J.  Hendrie  Lloyd,  Philadelphia. 
George  Roe  Lockwood,  New  York. 
Henry  M.  Lyman,  Chicago. 
Francis  T.  Miles,  Baltimore. 
Charles  K.  Mills,  Philadelphia. 
John  H.  Musser,  Philadelphia. 
Thomas  R.  Neilson,  Philadelphia. 
W.  P.  Northrup,  New  York. 
William  Osier,  Baltimore. 
Frederick  A.  Packard,  Philadelphia. 
William  Pepper,  Philadelphia. 
Frederick  Peterson,  New  York. 
W.  T.  Plant,  Syracuse,  New  York. 
William  M.  Powell,  Atlantic  City. 
B.  Alexander  Randall,  Philadelphia. 
Edward  O.  Shakespeare,  Philadelphia. 
F.  C.  Shattuck,  Boston. 
J.  Lewis  Smith,  New -York. 
Louis  Starr,  Philadelphia. 
M.  Allen  Starr,  New  York. 
J.  Madison  Taylor,  Philadelphia. 
Charles  W.  Townsend,  Boston. 
James  Tyson,  Philadelphia. 
W.  S.  Thayer,  Baltimore. 
Victor  C.  Vaughan,  Ann  Arbor,  Mich. 
Thompson  S.  Westcott,  Philadelphia. 
Henry  R.  Wharton,  Philadelphia. 
J.  William  White,  Philadelphia. 
J.  C.  Wilson,  Philadelphia. 


IV.   B.   SAUNDERS' 


For  Sale  by  Subscription. 


AN  AMERICAN  TEXT-BOOK  OF  GYNECOLOGY,  MEDICAL 
AND  SURGICAL,  for  the  use  of  Students  and  Practitioners. 
Edited  by  J.  M.  BALDY,  M.  D.  Forming  a  handsome  royal-octavo  volume, 
with  360  illustrations  in  text  and  37  colored  and  half-tone  plates.  Prices : 
Cloth,  $6.00  net ;  Sheep,  $7.00  net ;  Half  Russia,  $8.00  net. 

In  this  volume  all  anatomical  descriptions,  excepting  those  essential  to  a  clear 
understanding  of  the  text,  have  been  omitted,  the  illustrations  being  largely  de- 
pended upon  to  elucidate  the  anatomy  of  the  parts.  This  work,  which  is 
thoroughly  practical  in  its  teachings,  is  intended,  as  its  title  implies,  to  be  a 
working  text-book  for  physicians  and  students.  A  clear  line  of  treatment  has 
been  laid  down  in  every  case,  and  although  no  attempt  has  been  made  to  dis- 
cuss mooted  points,  still  the  most  important  of  these  have  been  noted  and  ex- 
plained. The  operations  recommended  are  fully  illustrated,  so  that  the  reader, 
having  a  picture  of  the  procedure  described  in  the  text  under  his  eye,  cannot  fail 
to  grasp  the  idea.  All  extraneous  matter  and  discussions  have  been  carefully 
excluded,  the  attempt  being  made  to  allow  no  unnecessary  details  to  cumber 
the  text.  The  subject-matter  is  brought  up  to  date  at  every  point,  and  the 
work  is  as  nearly  as  possible  the  combined  opinions  of  the  ten  specialists  who 
figure  as  the  authors. 

The  work  is  well  illustrated  throughout  with  wood-cuts,  half-tone  and 
colored  plates,  mostly  selected  from  the  authors'  private  collections. 


CONTRIBUTORS : 


Dr.  Henry  T.  Byford. 
John  M.  Baldy. 
Edwin  Cragin. 
J.  H.  Etheridge. 
William  Goodell. 


Dr.  Howard  A.  Kelly. 
Florian  Krug. 
E.  E.  Montgomery. 
William  R.  Pryor. 
George  M.  Tuttle. 


"The  most  notable  contribution  to  gynecological  literature  since  1887,  ....  and  the  most 
complete  exponent  of  gynecology  which  we  have.  No  subject  seems  to  have  been  neglected, 
....  and  the  gynecologist  and  surgeon,  and  the  general  practitioner  who  has  any  desire 
to  practise  diseases  of  women,  will  find  it  of  practical  value.  In  the  matter  of  illustrations 
and  plates  the  book  surpasses  anything  we  have  seen." — Boston  Medical  and  Surgical 
Journal . 

"  A  valuable  addition  to  the  literature  of  Gynecology.  The  writers  are  progressive, 
aggressive,  and  earnest  in  their  convictions."— Medical  News,  Philadelphia. 

"  A  thoroughly  modern  text-book,  and  gives  reliable  and  well-tempered  advice  and  in- 
struction."— Edinburgh  Medical  Journal. 

"  The  harmony  of  its  conclusions  and  the  homogeneity  of  its  style  give  it  an  individuality 
which  suggests  a  single  rather  than  a  multiple  authorship." — Annals  of  Surgery. 

'I  It  must  command  attention  and  respect  as  a  worthy  representation  of  our  advanced 
clinical  teaching." — American  Journal  of  Medical  Sciences. 


CATALOGUE    OF  MEDICAL    WORKS. 


For  Sale  by  Subscription. 


DISEASES  OF  THE  EYE.  A  Handbook  of  Ophthalmic  Prac- 
tice. By  G.  E.  DE  SCHWEINITZ,  M.  D.,  Professor  of  Diseases  of  the  Eye, 
Philadelphia  Polyclinic;  Professor  of  Clinical  Ophthalmology,  Jefferson 
Medical  College,  Philadelphia,  etc.  Forming  a  handsome  royal-octavo 
volume  of  more  than  600  pages,  with  over  200  fine  wood-cuts,  many  of 
which  are  original,  and  2  chromo-lithographic  plates.  Prices :  Cloth, 
$4.00  net;  Sheep,  $5.00  net;  Half  Russia,  $5.50  net. 

The  object  of  this  work  is  to  present  to  the  student  and  practitioner  who  is 
beginning  work  in  the  fields  of  ophthalmology  a  plain  description  of  the  optical 
defects  and  diseases  of  the  eye.  To  this  end  special  attention  has  been  paid 
to  the  clinical  side  of  the  question;  and  the  method  of  examination,  the  symp- 
tomatology leading  to  a  diagnosis,  and  the  treatment  of  the  various  ocular  defects 
have  been  brought  into  special  prominence.  The  general  plan  of  the  book  is 
eminently  practical.  Attention  is  called  to  the  large  number  of  illustrations 
(nearly  one-third  of  which  are  new),  which  will  materially  facilitate  the  thorough 
understanding  of  the  subject. 

"For  the  student  and  practitioner  it  is  the  best  single  volume  at  present  published." — 
Medical  News,  Philadelphia. 

"  A  most  complete  and  sterling  presentation  of  the  present  status  of  modern  knowledge 
concerning  diseases  of  the  eye." — Medical  Age. 

"  Pre-eminently  a  book  for  those  wishing  a  clear  yet  comprehensive  and  full  knowledge 
of  the  fundamental  truths  which  underlie  and  govern  the  practice  of  ophthalmology." — Med- 
ical and  Surgical  Reporter. 

"At  once  comprehensive  and  thoroughly  up  to  date." — Hospital  Gazette  (London). 

PROFESSIONAL  OPINIONS. 

"  A  work  that  will  meet  the  requirements  not  only  of  the  specialist,  but  of  the  general 
practitioner  in  a  rare  degree.  I  am  satisfied  that  unusual  success  awaits  it." 

WILLIAM  PEPPER,  M.  D., 

Provost  and  Professor  of  Theory  and  Practice  of  Medicine  and  Clinical  Medicine 
in  the  University  of  Pennsylvania. 

"Contains  in  concise  and  reliable  form  the  accepted  views  of  Ophthalmic  Science." 

WILLIAM  THOMSON,  M.  D., 
Professor  of  Ophthalmology,  Jefferson  Medical  College,  Philadelphia,  Pa. 

"  Contains  in  the  most  attractive  and  'easily  understood  form  just  the  sort  of  knowledge 
which  is  necessary  to  the  intelligent  practice  of  general  medicine  and  surgery." 

J.  WILLIAM  WHITE,  M.  D., 
Professor  of  Clinical  Surgery  in  the  University  of  Pennsylvania. 

"A  very  reliable  guide  to  the  study  of  eye  diseases,  presenting  the  latest  facts  and  newest 
ideas." 

SWAN  M.  BURNETT,  M.  D., 

Professor  of  Ophthalmology  and  Otology,  Medical  Department  Univ.  of  Georgetown, 

Washington,  D.  C. 


6  W.   B.   SAUNDERS' 


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MEDICAL  DIAGNOSIS.  By  Dr.  OSWALD  VIERORDT,  Professor  of 
Medicine  at  the  University  of  Heidelberg.  Translated,  with  additions, 
.  from  the  Second  Enlarged  German  Edition,  with  the  author's  permission, 
by  FRANCIS  H.  STUART,  A.  M.,  M.  D.  Third  and  Revised  Edition.  In 
one  handsome  royal-octavo  volume  of  700  pages,  178  fine  wood-cuts  in 
text,  many  of  which  are  in  colors.  Prices  :  Cloth,  $4.00  net;  Sheep,  $5.00 
net;  Half  Russia,  $5.50  net. 

In  this  work,  as  in  no  other  hitherto  published,  are  given  full  and  accurate 
explanations  of  the  phenomena  observed  at  the  bedside.  It  is  distinctly  a  clin- 
ical work  by  a  master  teacher,  characterized  by  thoroughness,  fulness,  and  accu- 
racy. It  is  a  mine  of  information  upon  the  points  that  are  so  often  passed  over 
without  explanation.  Especial  attention  has  been  given  to  the  germ-theory  as 
a  factor  in  the  origin  of  disease. 

This  valuable  work  is  now  published  in  German,  English,  Russian,  and 
Italian.  The  issue  of  a  third  American  edition  within  two  years  indicates  the 
favor  with  which  it  has  been  received  by  the  profession. 

"  Rarely  is  a  book  published  with  which  a  reviewer  can  find  so  little  fault  as  with  the 
volume  before  us.  All  the  chapters  are  full,  and  leave  little  to  be  desired  by  the  reader. 
Each  particular  item  in  the  consideration  of  an  organ  or  apparatus,  which  is  necessary  to 
determine  a  diagnosis  of  any  disease  of  that  organ,  is  mentioned;  nothing  seems  forgotten. 
The  chapters  on  diseases  of  the  circulatory  and  digestive  apparatus  and  nervous  system  are 
especially  full  and  valuable.  Notwithstanding  a  few  minor  errors  in  translating,  which  are 
of  small  importance  to  the  accuracy  of  the  rest  of  the  volume,  the  reviewer  would  repeat  that 
the  book  is  one  of  the  best — probably  the  best — which  has  fallen  into  his  hands.  An  excel- 
lent and  comprehensive  index  of  nearly  one  hundred  pages  closes  the  volume." — University 
Medical  Magazine,  Philadelphia. 

"Thorough  and  exact The  author  has  rendered  no  mean  service  to  medicine  in 

having  prepared  a  work  which  proves  as  useful  to  the  teacher  as  to  the  student  and  prac- 
titioner."— The  Lancet  (London). 

PROFESSIONAL.  OPINIONS. 

"  One  of  the  most  valuable  and  useful  works  in  medical  literature." 

ALEXANDER  J.  C.  SKENE,  M.  D., 

Dean  of  the  \Long  Island  College  Hospital,  and  Professor  of  the  Medical  and  Surgical 

Diseases  of  Women. 

"  Indispensable  to  both  '  students  and  practitioners.'  " 

F.  MINOT,  M.  D., 
Hersey  Professor  of  Theory  and  Practice  of  Medicine,  Harvard  University. 

"  It  is  very  well  arranged  and  very  complete,  and  contains  valuable  features  not  usually 
found  in  the  ordinary  books." 

J.  H.  MUSSER,  M.  D., 
Assistant  Professor  Clinical  Medicine,  University  of  Pennsylvania. 

"  One  of  the  most  valuable  works  now  before  the  profession,  both  for  study  and  reference." 

N.  S.  DAVIS,  M.  D., 

Professor  of  Principles  and  Practice  of  Medicine  and  Clinical  Medicine,  Chicago 

Medical  College. 


CATALOGUE    OF  MEDICAL    WORKS. 


For  Sale  by  Subscription. 

A  NEW  PRONOUNCING  DICTIONARY  OF  MEDICINE,  with 
Phonetic  Pronunciation,  Accentuation,  Etymology,  etc.  By  JOHN 
M.  KEATING,  M.  D.,  LL.D.,  Fellow  of  the  College  of  Physicians  of  Phila- 
delphia; Vice-President  of  the  American  Paediatric  Society;  Ex-President 
of  the  Association  of  Life  Insurance  Medical  Directors ;  Editor  "  Cyclo- 
paedia of  the  Diseases  of  Children,"  etc. ;  and  HENRY  HAMILTON,  author 
of  "  A  New  Translation  of  Virgil's  ^Eneid  into  English  Rhyme ;"  co- 
author of  "  Saunders'  Medical  Lexicon,"  etc.;  with  the  Collaboration  of 
J.  CHALMERS  DACOSTA,  M.  D.,  and  FREDERICK  A.  PACKARD,  M.  D. 
With  an  Appendix  containing  important  Tables  of  Bacilli,  Micrococci, 
Leucomames,  Ptomaines,  Drugs  and  Materials  used  in  Antiseptic  Sur- 
gery, Poisons  and  their  Antidotes,  Weights  and  Measures,  Thermometric 
Scales,  New  Official  and  Unofficial  Drugs,  etc.  Forming  one  very 
attractive  volume  of  over  800  pages.  Second  Revised  Edition.  Prices : 
Cloth,  $5.00  net;  Sheep,  $6.00  net;  Half  Russia,  $6.50  net.  With 
Denison's  Patent  Index  for  Ready  Reference. 

PROFESSIONAL  OPINIONS. 

"  I  am  much  pleased  with  Keating's  Dictionary,  and  shall  take  pleasure  in  recommending 
it  to  my  classes.'* 

HENRY  M.  LYMAN,  M.  D.. 

Professor  of  Principles  and  Practice  of  Medicine,  Rush  Medical  College,  Chicago,  III. 
"  I  am  convinced  that  it  will  be  a  very  valuable  adjunct  to  my  study-table,  convenient  in 
size  and  sufficiently  full  for  ordinary  use." 

C.  A.  LlNDSLEY,  M.   D., 

Professor  of  Theory  and  Practice  of  Medicine,  Medical  Dept.  Yale  University; 

Secretary  Connecticut  State  Board  of  Health,  New  Haven,  Conn, 

"I  will  point  out  to  my  classes  the  many  good  features  of  this  book  as  compared  with 
others,  which  will,  I  am  sure,  make  it  very  popular  with  students." 

JOHN  CRONYN,  M.  D./LL.D., 
Professor  of  Principles  and  Practice  of  Medicine  and  Clinical  Medicine ; 

President  of  the  Faculty,  Medical  Dept.  Niagara  University,  Buffalo,  N.  Y. 

AUTOBIOGRAPHY  OF  SAMUEL  D.  GROSS,  M.  D.,  Emeritus  Pro- 
fessor of  Surgery  in  the  Jefferson  Medical  College  of  Philadelphia,  with 
Reminiscences  of  His  Times  and  Contemporaries.  Edited  by  his  sons, 
SAMUEL  W.  GROSS,  M.  D.,  LL.D.,  late  Professor  of  Principles  of  Surgery 
and  of  Clinical  Surgery  in  the  Jefferson  Medical  College,  and  A.  HALLER 
GROSS,  A.  M.,  of  the  Philadelphia  Bar.  Preceded  by  a  Memoir  of  Dr. 
Gross,  by  the  late  Austin  Flint,  M.  D.,  LL.D.  In  two  handsome  volumes, 
each  containing  over  400  pages,  demy  8vo,  extra  cloth,  gilt  tops,  with  fine 
Frontispiece  engraved  on  steel.  Price,  $5.00  net. 

This  autobiography,  which  was  continued  by  the  late  eminent  surgeon  until 
within  three  months  of  his  death,  contains  a  full  and  accurate  history  of  his 
early  struggles,  trials,  and  subsequent  successes,  told  in  a  singularly  interesting 
and  charming  manner,  and  embraces  short  and  graphic  pen-portraits  of  many 
of  the  most  distinguished  men — surgeons,  physicians,  divines,  lawyers,  states- 
men, scientists,  etc. — with  whom  he  was  brought  in  contact  in  America  and  in 
Europe  :  the  whole  forming  a  retrospect  of  more  than  three-quarters  of  a  century. 


W.   B.   SAUNDERS' 


For  Sale  by  Subscription. 


AN  AMERICAN  TEXT-BOOK  OF  OBSTETRICS.  By  American 
Teachers.  By  Richard  C.  Norris,  A.  M.,  M.  D.;  James  H.  Etheridge, 
M.  D. ;  Chauncey  D.  Palmer,  M.  D. ;  Howard  A.  Kelly,  M.  D. ;  Charles 
Jewett,  M.  D. ;  Henry  J.  Garrigues,  M.  D. ;  Barton  Cooke  Hirst,  M.  D.; 
Theophilus  Parvin,  M.  D. ;  George  A.  Piersol,  M.  D. ;  Edward  P.  Davis, 
M.  D. ;  Charles  Warrington  Earle,  M.  D. ;  Robert  L.  Dickinson,  M.  D. ; 
Edward  Reynolds,  M.  D. ;  Henry  Schwarz,  M.  D. ;  and  James  C.  Cam- 
eron, M.  D.  In  one  very  handsome  imperial-octavo  volume,  with  a  large 
number  of  original  illustrations,  including  full-page  plates,  and  uniform 
with  "  The  American  Text- Book  of  Gynecology."  (In  active  preparation.) 

Such  an  array  of  well-known  teachers  is  a  sufficient  guarantee  of  the  high 
character  of  the  work,  and  it  gives  the  assurance  that  this  work  will  have  the 
same  measure  of  success  awarded  it  as  has  attended  the  recent  publication  of 
its  companion  volume,  "  The  American  Text-Book  of  Gynecology."  The  illus- 
trations will  receive  the  most  minute  attention ;  the  cuts  interspersed  throughout 
the  text,  and  the  full-page  plates,  which  will  reflect  the  highest  attainments  of 
the  artist  and  engraver,  will  appeal  at  once  to  the  eye  as  well  as  to  the  mind 
of  the  student  and  practitioner. 

AN  AMERICAN  TEXT-BOOK  OF  PHYSIOLOGY.  By  American 
Teachers.  Edited  by  WILLIAM  H.  HOWELL,  PH.  D.,  M.  D.,  Professor 
of  Physiology,  Johns  Hopkins  University.  With  the  collaboration  of  such 
eminent  specialists  as  Henry  P.  Bowditch,  M.  D. ;  John  G.  Curtis,  M.  D. ; 
Henry  H.  Donaldson,  M.  D. ;  Frederick  S.  Lee,  M.  D. ;  Warren  P.  Lom- 
bard, A.  B.,  M.  D. ;  Graham  Lusk,  PH.  D. ;  Henry  Sewall,  M.  D. ;  Edward 
T.  Reichert,  M.  D. ;  Joseph  W.  Warren,  M.  D.  In  one  imperial-octavo 
volume  (with  a  large  number  of  original  illustrations),  uniform  with  The 
American  Text-Books  of  "Surgery,"  "Practice,"  "Gynecology,"  etc. 
(In  preparation  for  early  publication.) 

This  will  be  the  most  notable  attempt  yet  made  in  thfs  country  to  combine  in 
one  volume  the  entire  subject  of  Human  Physiology  by  well-known  teachers 
who  have  given  especial  study  to  that  part  of  the  subject  upon  which  they  will 
write.  The  completed  work  will  represent  the  present  status  of  the  science  of 
Physiology,  and  in  particular  from  the  standpoint  of  the  student  of  medicine 
and  the  medical  practitioner.  Illustrations  largely  drawn  from  original  sources 
will  be  used  freely  throughout  the  text. 

AN  AMERICAN  TEXT-BOOK  OF  APPLIED  THERAPEUTICS. 
By  American  Teachers.  (In  preparation.) 

AN  AMERICAN  TEXT-BOOK  OF  NURSING.  By  American 
Teachers.  (In  preparation.) 


CATALOGUE    OF  MEDICAL    WORKS. 


A  SYLLABUS  OF  GYN^COLOGY,  arranged  in  conformity  with 
The  American  Text-Book  of  Gynecology.  By  J.  W.  LONG,  M.  D., 
Professor  of  Diseases  of  Women  and  Children,  Medical  College  of  Vir- 
ginia, etc.  (Preparing.) 

Based  upon  the  teaching  and  methods  laid  down  in  the  larger  work,  this  will 
not  only  be  useful  as  a  supplementary  volume,  but  to  those  who  do  not  already 
possess  the  text-book  it  will  also  have  an  independent  value  as  an  aid  to  the 
practitioner  in  gynecological  work,  and  to  the  student  as  a  guide  in  the  lecture- 
room,  as  the  subject  is  presented  in  a  manner  at  once  systematic,  clear,  succinct, 
and  practical. 


TEMPERATURE  CHART.     Prepared  by  D.  T.  LAINE,  M.  D.      Size 
8x  13/4  inches.     Price,  per  pad  of  25  charts,  50  cents. 

A  conveniently  arranged  chart  for  recording  Temperature,  with  columns  for 
daily  amounts  of  Urinary  and  Fecal  Excretions,  Food,  Remarks,  etc.  On  the 
back  of  each  chart  is  given  in  full  the  method  of  Brand  in  the  treatment  of 
Typhoid  Fever. 


THE  NURSE'S  DICTIONARY  of  Medical  Terms  and  Nursing 
Treatment,  containing  Definitions  of  the  Principal  Medical  and  Nursing 
Terms,  Abbreviations,  and  Physiological  Names,  and  Descriptions  of  the 
Instruments,  Drugs,  Diseases,  Accidents,  Treatments,  Operations,  Foods, 
Appliances,  etc.  encountered  in  the  ward  or  in  the  sick-room.  Compiled 
for  the  use  of  nurses.  By  HONNOR  MORTEN,  author  of  "  How  to  Become 
a  Nurse,"  "  Sketches  of  Hospital  Life,"  etc.  Second  and  enlarged  edi- 
tion. i6mo,  140  pages.  Price,  Cloth,  $1.00. 

This  little  volume  is  intended  for  use  merely  as  a  small  re  fere  nee -book  which 
can  be  consulted  at  the  bedside  or  in  the  ward.  It  gives  sufficient  explanation 
to  the  nurse  to  enable  her  to  comprehend  a  case  until  she  has  leisure  to  look 
up  larger  and  fuller  works  on  the  subject. 

"  Should  be  at  the  disposal  of  every  nurse." — Birmingham  Medical  Review. 

"  Maintains  its  reputation  for  brevity  and  simplicity." — Hahnemannian  Monthly. 

"Though  ostensibly  for  professional  nurses,  contains  in  a  compact  form  just  such  infor- 
mation as  almost  every  intelligent  man  would  like  to  have  at  hand  in  these  (days  when 
the  interest  in  all  matters  of  sanitation  and  medicine  has  become  so  great." — Medical 
Examiner. 

"  A  book  which  every  progressive  nurse  must  have." — Medical  World. 

"  This  little  volume  is  almost  indispensable  in  the  training  school  and  in  the  library  of  the 
nurse." — Neiv  York  Medical  Times. 


IO  W.   B.   SAUNDERS* 


SURGICAL  PATHOLOGY  AND  THERAPEUTICS.  By  J.  COL- 
LINS WARREN,  M.  D.,  Professor  of  Surgery,  Harvard  Medical  School,  etc. 
In  one  very  handsome  octavo  volume  of  over  800  pages,  with  135  illus- 
trations, 33  of  which  are  chromo-lithographs,  and  all  of  which  are  drawn 
from  original  specimens.  (Passing  through  the  press.) 

Covering  as  it  does  the  entire  field  of  Surgical  Pathology  and  Surgical  Thera- 
peutics by  an  acknowledged  authority,  the  publisher  is  confident  that  the  work 
will  rank  as  a  standard  authority  on  the  subject  of  which  it  treats.  Particular 
attention  has  been  paid  to  Bacteriology  and  Surgical  Bacteria  from  the  stand- 
point of  recent  investigations,  and  the  chromo-lithographic  plates  in  their  fidelity 
to  nature  and  in  scientific  accuracy  have  hitherto  been  unapproached. 

DISEASES  OF  WOMEN.  By  HENRY  J.  GARRIGUES,  A.M.,  M.D., 
Professor  of  Obstetrics  in  the  New  York  Post-Graduate  Medical  School 
and  Hospital;  Gynecologist  to  St.  Mark's  Hospital  and  to  the  German 
Dispensary,  etc.,  New  York  City.  In  one  very  handsome  octavo  volume 
of  about  700  pages,  illustrated  by  numerous  wood-cuts  and  colored  plates. 
Prices:  Cloth,  $4.00  net ;  Sheep,  $5. oo  net. 

A  PRACTICAL  work  on  gynecology  for  the  use  of  students  and  practitioners, 
written  in  a  terse  and  concise  manner.  The  importance  of  a  thorough  know- 
ledge of  the  anatomy  of  the  female  pelvic  organs  has  been  fully  recognized  by 
the  author,  and  considerable  space  has  been  devoted  to  the  subject.  The  chap- 
ters on  Operations  and  on  Treatment  are  thoroughly  modern,  and  are  based 
upon  the  large  hospital  and  private  practice  of  the  author.  The  text  is  eluci- 
dated by  a  large  number  of  illustrations  and  colored  plates,  many  of  them  being 
original,  and  forming  a  complete  atlas  for  studying  embryology  and  the  anatomy 
of  \ht  female  genitalia,  besides  exemplifying,  whenever  needed,  morbid  condi- 
tions, instruments,  apparatus,  and  operations. 

EXCERPT   OF   CONTENTS. 

Development  of  the  Female  Genitals. — Anatomy  of  the  Female  Pelvic  Organs. — Phys- 
iology.— Puberty. — Menstruation  and  Ovulation. — Copulation.— Fecundation. — The  Climac- 
teric.— Etiology  in  General. — Examinations  in  General. — Treatment  in  General — Abnormal 
Menstruation  and  Metrorrhagia. — Leucorrhea. — Diseases  of  the  Vulva. — Diseases  of  the 
Perineum. — Diseases  of  the  Vagina. — Diseases  of  the  Uterus. — Diseases  of  the  Fallopian 
Tubes.— Diseases  of  the  Ovaries.— Diseases  of  the  Pelvis.— Sterility. 

The  reception  accorded  to  this  work  has  been  most  flattering.  In  the  short 
period  which  has  elapsed  since  its  issue  it  has  been  adopted  and  recommended 
as  a  text-book  by  more  than  60  of  the  Medical  Schools  and  Universities  of  the 
United  States  and  Canada. 

"One  of  the  best  text-books  for  students  and  practitioners  which  has  been  published  in 
the  English  language;  it  is  condensed,  clear,  and  comprehensive.  The  profound  learning 
and  great  clinical  experience  of  the  distinguished  author  find  expression  in  this  book  in  a 
most  attractive  and  instructive  form.  Young  practitioners,  to  whom  experienced  consultants 
may  not  be  available,  will  find  in  this  book  invaluable  counsel  and  help." 

THAD.  A.  RHAMY,  M.  D.,  LL.D., 

Professor  of  Clinical  Gynecology,  Medical  College  of  Ohio  ;  Gynecologist  to  the  Good 
Samaritan  and  Cincinnati  Hospitals. 


Practical,  Exhaustive,  Authoritative. 


SAUNDERS' 

NEW  AID  SERIES  OF  MANUALS 


FOR 


Students  and  Practitioners. 


MR.  SAUNDERS  is  pleased  to  announce  as  in  active  preparation  his  NEW 
AID  SERIES  OF  MANUALS  for  Students  and  Practitioners.  As 
publisher  of  the  STANDARD  SERIES  OF  QUESTION  COMPENDS,  and  through  in- 
timate relations  with  leading  members  of  the  medical  profession,  Mr.  Saunders 
has  been  enabled  to  study  progressively  the  essential  desiderata  in  practical 
"self-helps"  for  students  and  physicians. 

This  study  has  manifested  that,  while  the  published  "  Question  Compends" 
earn  the  highest  appreciation  of  students,  whom  they  serve  in  reviewing  their 
studies  preparatory  to  examination,  there  is  special  need  of  thoroughly  reliable 
handbooks  on  the  leading  branches  of  Medicine  and  Surgery,  each  subject 
being  compactly  and  authoritatively  written,  and  exhaustive  in  detail,  without 
the  introduction  of  cases  and  foreign  subject-matter  which  so  largely  expand 
ordinary  text-books. 

The  Saunders  Aid  Series  will  not  merely  be  condensations  from 
present  literature,  but  will  be  ably  written  by  well-known  authors 
and  practitioners,  most  of  them  being  teachers  in  representative 
American  Colleges.  This  new  series,  therefore,  will  form  an  admirable 
collection  of  advanced  lectures,  which  will  be  invaluable  aids  to  students  in 
reading  and  in  comprehending  the  contents  of  "recommended"  works. 

Each  Manual  will  further  be  distinguished  by  the  beauty  of  the  new  type ; 
by  the  quality  of  the  paper  and  printing ;  by  the  copious  use  of  illustrations ; 
by  the  attractive  binding  in  cloth ;  and  by  the  extremely  low  price,  which 
will  uniformly  be  $1.25  per  volume. 

II 


SAUNDERS'  NEW  AID  SERIES  OF  MANUALS, 


VOLUMES  NOW  READY, 


PHYSIOLOGY.  By  JOSEPH  HOWARD  RAYMOND,  A.  M.,  M.  D.,  Professor 
of  Physiology  and  Hygiene  and  Lecturer  on  Gynecology  in  the  Long 
Island  College  Hospital,  etc.  Price,  $1.25  net. 

SURGERY,  General  and  Operative.  By  JOHN  CHALMERS  DACOSTA, 
M.  D,,  Demonstrator  of  Surgery,  Jefferson  Medical  College,  Philadelphia, 
etc.  Double  number.  Price,  $2.50  net. 

DOSE-BOOK  AND  MANUAL  OF  PRESCRIPTION-WRITING. 
By  E.  Q.  THORNTON,  M.  D.,  Demonstrator  of  Therapeutics,  Jefferson 
Medical  College,  Philadelphia.  Price,  $1.25  net. 

MEDICAL  JURISPRUDENCE.  By  HENRY  C.  CHAPMAN,  M.  D.,  Pro- 
fessor of  Institutes  of  Medicine  and  Medical  Jurisprudence  in  the  Jeffer- 
son Medical  College  of  Philadelphia,  etc  Price,  $1.25  net. 

SURGICAL  ASEPSIS.  By  CARL  BECK,  M.D.,  Surgeon  to  St.  Mark's 
Hospital  and  to  the  German  Poliklinik ;  Instructor  in  Surgery,  New  York 
Post-Graduate  Medical  School,  etc.  Price,  $1.2$  net. 


VOLUMES  IN  PREPARATION  TOR  EARLY  PUBLICATION, 

OBSTETRICS.  By  W.  A.  NEWMAN  DORLAND,  M.  D.,  Demonstrator  of 
Obstetrics,  University  of  Pennsylvania;  Chief  of  Gynecological  Dispen- 
sary, Pennsylvania  Hospital ;  Member  of  Philadelphia  Obstetrical  Society, 
etc.  Price,  $1.25  net. 

MATERIA  MEDICA  AND  THERAPEUTICS.  By  HENRY  A. 
GRIFFIN,  A.  B.,  M.  D.,  Assistant  Physician  to  the  Roosevelt  Hospital, 
Out-patient  Department,  New  York  City.  Price,  $1.25  net. 

SYPHILIS  AND  THE  VENEREAL  DISEASES.  By  JAMES 
NEVINS  HYDE,  M.  D.,  Professor  of  Skin  and  Venereal  Diseases  in  Rush 
Medical  College,  Chicago.  Double  number.  Price,  $2.50  net. 

NERVOUS  DISEASES.  By  CHARLES  W.  BURR,  M.  D.,  Clinical  Pro- 
fessor of  Nervous  Diseases,  Medico-Chirurgical  College,  Philadelphia, 
etc.  Price,  $1.25  net. 

PRACTICE  OF  MEDICINE.  By  GEORGE  ROE  LOCKWOOD,  M.  D., 
Professor  of  Practice  in  the  Woman's  Medical  College  and  in  the  New 
York  Infirmary,  etc.  Double  number.  Price,  $2.50  net. 

NOSE  AND  THROAT.  By  D.  BRADEN  KYLE,  M.  D.,  Chief  Laryngol- 
ogist  to  St.  Agnes'  Hospital,  Philadelphia;  Instructor  in  Clinical  Micros- 
copy and  Assistant  Demonstrator  of  Pathology  in  the  Jefferson  Medical 
College,  etc.  Price,  $1.25  net. 

%*  There  will  be  published  in  the  same  series,  at  close  intervals,  carefully-pre- 
pared works  on  the  subjects  of  Anatomy,  Gynecology,  Pathology,  Hygiene,  etc., 
by  prominent  specialists. 
12 


CA7^ALOGUE    OF  MEDICAL    WORKS.  13 

Saunders'  New  Aid  Series  of  Manuals. 


A  MANUAL  OF  PHYSIOLOGY.  By  JOSEPH  H.  RAYMOND,  A.  M., 
M.D.,  Professor  of  Physiology  and  Hygiene  and  Lecturer  on  Gynecology 
in  the  Long  Island  College  Hospital ;  Director  of  Physiology  in  the  Hoag- 
land  Laboratory;  formerly  Lecturer  on  Physiology  and  Hygiene  in  the 
Brooklyn  Normal  School  for  Physical  Education;  Ex- Vice -President  of 
the  American  Public  Health  Association;  Ex-Health  Commissioner  City 
of  Brooklyn,  etc.  Illustrated.  Price,  Cloth,  $1.25  net.  (Just  ready.) 

In  this  manual  the  author  has  endeavored  to  put  into  a  concrete  and  avail- 
able form  the  results  of  twenty  years'  experience  as  a  teacher  of  Physiology  to 
medical  students,  and  has  produced  a  work  for  the  student  and  practitioner, 
representing  in  a  concise  form  the  existing  state  of  Physiology  and  its  methods 
of  investigation,  based  upon  Comparative  and  Pathological  Anatomy,  Clinical 
Medicine,  Physics,  and  Chemistry,  as  well  as  upon  experimental  research. 


A  MANUAL  OF  SURGERY,  General  and  Operative.  By  JOHN 
CHALMERS  DACOSTA,  M.  D.,  Demonstrator  of  Surgery,  Jefferson  Medical 
College,  Philadelphia ;  Chief  Assistant  Surgeon,  Jefferson  Medical  College 
Hospital ;  Surgical  Registrar,  Philadelphia  Hospital,  etc.  One  very  hand- 
some volume  of  over  700  pages,  with  a  large  number  of  illustrations. 
(Double  number.)  Price,  Cloth,  $2.50  net. 


A  new  manual  of  the  Principles  and  Practice  of  Surgery,  intended  to  meet 
the  demands  of  students  and  working  practitioners  for  a  medium-sized  work 
which  will  embody  all  the  newer  methods  of  procedure  detailed  in  the  larger 
text-books.  The  work  has  been  written  in  a  concise,  practical  manner,  and 
especial  attention  has  been  given  to  the  most  recent  methods  of  treatment. 
Illustrations  are  freely  used  to  elucidate  the  text. 


A  MANUAL  OF  OBSTETRICS.  By  W.  A.  NEWMAN  DORLAND, 
M.  D.,  Demonstrator  of  Obstetrics,  University  of  Pennsylvania;  Chief  of 
Gynecological  Dispensary,  Pennsylvania  Hospital;  Member  of  Phila- 
delphia Obstetrical  Society,  etc.  Profusely  illustrated.  Price,  Cloth, 
$1.2$  net.  (Preparing.) 

This  work,  which  is  thoroughly  practical  in  its  teachings,  is  intended,  as  its 
title  implies,  to  be  a  working  text-book  for  the  student  and  of  value  to  the 
practitioner  as  a  convenient  handbook  of  reference.  Although  concisely  writ- 
ten, nothing  of  importance  is  omitted  that  will  give  a  clear  and  succinct  know- 
ledge of  the  subject  as  it  stands  to-day.  Illustrations  are  freely  used  throughout 
the  text. 


14  W.   B.    SAUNDERS' 


Sannders9  New  Aid  Series  of  Manuals. 


DOSE-BOOK  AND  MANUAL  OF  PRESCRIPTION-WRITING. 
By  E.  Q.  THORNTON,  M.  D.,  Demonstrator  of  Therapeutics,  Jefferson 
Medical  College,  Philadelphia.  Illustrated.  Price,  Cloth,  £1.25  net. 

But  little  attention  is  generally  given,  in  works  on  Materia  Medica  and  Thera- 
peutics, to  the  methods  of  combining  remedies  in  the  form  of  prescriptions,  and 
this  manual  has  been  written  especially  for  students  in  the  hope  that  it  may 
serve  to  give  a  thorough  and  comprehensive  knowledge  of  the  subject. 

The  work,  which  is  based  upon  the  last  (1890)  edition  of  the  Pharmacopeia^ 
fully  covers  the  subjects  of  Weights  and  Measures,  Prescriptions  (form  of 
writing,  general  directions  to  pharmacist,  grammatical  construction,  etc.), 
Dosage,  Incompatibles,  Poisons,  etc. 

MEDICAL  JURISPRUDENCE  AND  TOXICOLOGY.  By  HENRY 
C.  CHAPMAN,  M.  D.,  Professor  of  Institutes  of  Medicine  and  Medical 
Jurisprudence  in  the  Jefferson  Medical  College  of  Philadelphia ;  Member 
of  the  College  of  Physicians  of  Philadelphia,  of  the  Academy  of  Natural 
Sciences  of  Philadelphia,  of  the  American  Philospphical  Society,  and  of 
the  Zoological  Society  of  Philadelphia.  232  pages,  with  36  illustrations, 
some  of  which  are  in  colors.  Price,  $1.25  net. 

For  many  years  there  has  been  a  demand  from  members  of  the  medical  and 
legal  professions  for  a  medium-sized  work  on  this  most  important  branch  of 
medicine.  The  necessarily  proscribed  limits  of  the  work  permit  the  considera- 
tion only  of  those  parts  of  this  extensive  subject  which  the  experience  of  the 
author  as  coroner's  physician  of  the  city  of  Philadelphia  for  a  period  of  six 
years  leads  him  to  regard  as  the  most  material  for  practical  purposes. 

Particular  attention  is  drawn  to  the  illustrations,  many  being  produced  in 
colors,  thus  conveying  to  the  layman  a  far  clearer  idea  of  the  more  intricate 
cases. 

"  The  salient  points  are  clearly  defined,  and  ascertained  facts  are  laid  down  with  a  clear- 
ness that  is  unequivocal." — St.  Louis  Medical  and  Surgical  Journal. 

"The  presentation  is  always  thorough,  the  text  is  liberally  interspersed  with  illustrations, 
and  the  style  of  the  author  is  at  once  pleasing  and  interesting." — Therapeutic  Gazette. 

"  One  that  is  not  overloaded  with  an  unnecessary  detail  of  a  large  amount  of  literature  on 
the  subject,  requiring  hours  of  research  for  the  essential  points  in  the  decision  of  a  question ; 
that  contains  the  most  lucid  symptomatology  of  questionable  conditions,  tests  of  poisons,  and 
the  readiest  means  of  making  them — such  is  the  new  book  before  us." — T/ie  Sanitarian. 

A  GUIDE  TO  THE  BACTERIOLOGICAL  LABORATORY.     By 

LANC.DON  FROTHINGUAM,  M.  D.     Illustrated.     (In  preparation.) 

The  technical  methods  involved  in  bacteria-culture,  methods  of  staining,  and 
microscopical  study  are  fully  described  and  arranged  as  simply  and  concisely 
as  possible.  The  book  is  especially  intended  for  use  in  laboratory  work. 


CATALOGUE    OF  MEDICAL    WORKS.  15 


NURSING:  ITS  PRINCIPLES  AND  PRACTICE.  By  ISABEL 
ADAMS  HAMPTON,  Graduate  of  the  New  York  Training  School  for 
Nurses  attached  to  Bellevue  Hospital;  Superintendent  of  Nurses  and 
Principal  of  the  Training  School  for  Nurses,  Johns  Hopkins  Hospital, 
Baltimore,  Md. ;  late  Superintendent  of  Nurses,  Illinois  Training  School 
for  Nurses,  Chicago,  111.  In  one  very  handsome  I2mo  volume  of  484 
pages,  profusely  illustrated.  Price,  Cloth,  $2.00  net. 

This  entirely  new  work  on  the  important  subject  of  nursing  is  at  once  com- 
prehensive and  sj'stematic.  It  is  written  in  a  clear,  accurate,  and  readable 
style,  suitable  alike  to  the  student  and  the  lay  reader.  Such  a  work  has  long 
been  a  desideratum  with  those  intrusted  with  the  management  of  hospitals  and 
the  instruction  of  nurses  in  training  schools.  It  is  also  of  especial  value  to  the 
graduated  nurse  who  desires  to  acquire  a  practical  working  knowledge  of  the. 
care  of  the  sick  and  the  hygiene  of  the  sick-room. 

The  author,  who  has  had  considerable  experience  as  superintendent  of 
training  schools  for  nurses  and  hospital  management,  brings  to  her  task  a  mind 
thoroughly  equipped  to  make  the  subject  attractive  as  well  as  scientific  and 
instructive. 

Thoroughly  attested  and  approved  processes  in  practical  nursing  only  have 
been  given,  particularly  in  antiseptic  surgery,  and  the  minutest  details  regard- 
ing the  nurse's  technique  have  been  explained. 

Illustrations  to  elucidate  the  text  have  been  used  freely  throughout  the  book, 
and  they  will  be  found  of  material  help  in  showing  the  forms  of  modern  appli- 
ances for  the  hospital  ward  and  sick-room,  the  registration  of  temperature,  daily 
records,  etc. 


METHODS  OF  PREVENTING  AND  CORRECTING  DEFORM- 
ITIES OF  THE  BONES  AND  JOINTS  :  A  Handbook  of  Prac- 
tical Orthopedic  Surgery.  By  H.  AUGUSTUS  WILSON,  M.  D  ,  Professor 
of  General  and  Orthopedic  Surgery,  Philadelphia  Polyclinic ;  Clinical  Pro- 
fessor of  Orthopedic  Surgery,  Jefferson  Medical  College,  Philadelphia,  etc. 
(In  preparation.) 

The  aim  of  the  author  is  to  provide  a  book  of  moderate  size,  containing 
comprehensive  details  that  will  enable  general  practitioners  to  understand  thor- 
oughly the  mechanical  features  of  the  many  forms  of  congenital  and  acquired 
deformities  of  the  bones  and  joints. 

The  mechanical  functions  that  are  impaired  will  be  considered  first  as  to  pre- 
vention as  of  primary  importance,  and  following  this  will  be  described  the 
methods  of  correction  that  have  been  proved  practical  by  the  author.  Ope- 
rative procedures  will  be  considered  from  a  mechanical  as  well  as  a  surgical 
standpoint.  Prominence  will  be  given  to  the  mechanical  requirements  for 
braces  and  artificial  limbs,  etc.,  with  description  of  the  methods  for  construct- 
ing the  simplest  forms,  whether  made  of  plaster  of  Paris,  felt,  leather,  paper, 
steel,  or  other  materials,  together  with  the  methods  of  readjustment  to  suit  the 
changes  occurring  during  the  progress  of  the  case.  A  very  large  number  of 
original  illustrations  will  be  used. 


1 6  w.   B.    SAUNDERS' 


AN  OPERATION  BLANK,  with  Lists  of  Instruments,  etc.  re- 
quired in  Various  Operations.  Prepared  by  W.  W.  KEEN,  M.  D., 
LL.D.,  Professor  of  Principles  of  Surgery  in  the  Jefferson  Medical  Col- 
lege, Philadelphia.  Price  per  Pad,  containing  Blanks  for  fifty  operations, 
50  cents  net. 

A  convenient  blank,  suitable  for  all  operations,  giving  complete  instructions 
regarding  necessary  preparation  of  patient,  etc.,  with  a  full  list  of  dressings  and 
medicines  to  be  employed. 

At  the  back  of  pad  is  a  list  of  instruments  used — viz.  general  instruments, 
etc.,  required  for  all  operations;  and  special  instruments  for  surgery  of  the 
brain  and  spine,  mouth  and  throat,  abdomen,  rectum,  male  and  female  genito- 
urinary organs,  the  bones,  etc. 

The  whole  forming  a  neat  pad,  arranged  for  hanging  on  the  wall  of  a  sur 
geon's  office  or  in  the  hospital  operating  room. 

"  Will  serve  a  useful  purpose  for  the  surgeon  in  reminding  him  of  the  details  of  prepa- 
ration for  the  patient  and  the  rcom  as  well  as  for  the  instruments,  dressings,  and  antiseptics 
needed  " — New  York  Medical  Record 

"  Covers  about  all  that  can  be  needed  in  any  operation." — American  Lancet. 
"  The  plan  is  a  capital  one." — Boston  Medical  and  Surgical  Journal. 


ESSENTIALS  OF  ANATOMY  AND  MANUAL  OF  PRACTI- 
CAL DISSECTION,  containing  "  Hints  on  Dissection  "  By  CHARLES 
B.  NANCREDE,  M.  D.,  Professor  of  Surgery  and  Clinical  Surgery  in  the 
University  of  Michigan,  Ann  Arbor;  Corresponding  Member  of  the  Royal 
Academy  of  Medicine,  Rome,  Italy ;  late  Surgeon  Jefferson  Medical  Col- 
lege, etc.  Fourth  and  revised  edition.  Post  8vo,  over  50x5  pages,  with 
handsome  full-page  lithographic  plates  in  colors,  and  over  200  illustrations. 
Price :  Extra  Cloth  or  Oilcloth  for  the  dissection-room,  $2.00  net. 

Neither  pains  nor  expense  has  been  spared  to  make  this  work  the  most  ex- 
haustive yet  concise  Student's  Manual  of  Anatomy  and  Dissection  ever  pub- 
lished, either  in  America  or  in  Europe. 

The  colored  plates  are  designed  to  aid  the  student  in  dissecting  the  muscles, 
arteries,  veins,  and  nerves.  The  wood-cuts  have  all  been  specially  drawn  and 
engraved,  and  an  Appendix  added  containing  60  illustrations  representing  the 
structure  of  the  entire  human  skeleton,  the  whole  being  based  on  the  eleventh 
edition  of  Gray's  Anatomy,  and  forming  a  handsome  post  Svo  volume  of  over 
500  pages. 

"  The  plates  are  of  more  than  ordinary  excellence,  and  are  of  especial  value  to  students  in 
their  work  in  the  dissecting-room."— Journal  of  American  Medical  Association. 

"  Should  be  in  the  hands  of  every  medical  student." — Cleveland  Medical  Gazette. 
"  A  concise  and  judicious  work." — Buffalo  Medical  and  Surgical  Journal. 


CATALOGUE    OF  MEDICAL    WORKS. 


A  MANUAL  OF  PRACTICE  OF  MEDICINE.  By  A.  A.  STEVENS, 
A.  M.,  M.  D.,  Instructor  of  Physical  Diagnosis  in  the  University  of  Penn- 
sylvania, and  Demonstrator  of  Pathology  in  the  Woman's  Medical  College 
of  Philadelphia.  Specially  intended  for  students  preparing  for  graduation 
and  hospital  examinations,  and  includes  the  following  sections :  General 
Diseases,  Diseases  of  the  Digestive  Organs,  Diseases  of  the  Respiratory 
System,  Diseases  of  the  Circulatory  System,  Diseases  of  the  Nervous  Sys- 
tem, Diseases  of  the  Blood,  Diseases  of  the  Kidneys,  and  Diseases  of  the 
Skin.  Each  section  is  prefaced  by  a  chapter  on  General  Symptomatology. 
Third  edition.  Post  8vo,  502  pages.  Numerous  illustrations  and  selected 
formulae.  Price,  $2.50. 

Contributions  to  the  science  of  medicine  have  poured  in  so  rapidly  during  the 
last  quarter  of  a  century  that  it  is  well-nigh  impossible  for  the  student,  with  the 
limited  time  at  his  disposal,  to  master  elaborate  treatises  or  to  cull  from  them 
that  knowledge  which  is  absolutely  essential.  From  an  extended  experience  in 
teaching,  the  author  has  been  enabled,  by  classification,  to  group  allied  symp- 
toms, and  by  the  judicious  elimination  of  theories  and  redundant  explanations 
to  bring  within  a  comparatively  small  compass  a  complete  outline  of  the  prac- 
tice of  medicine. 


A  SYLLABUS  OF  LECTURES  ON  THE  PRACTICE  OF  SUR- 
GERY, arranged  in  conformity  with  The  American  Text-Book  of 
Surgery.  By  NICHOLAS  SENN,  M.  D.,  PH.  D.,  Professor  of  Surgery  in 
Rush  Medical  College,  Chicago,  and  in  the  Chicago  Polyclinic.  Price, 
$2.00. 

This,  the  latest  work  of  its  eminent  author,  himself  one  of  the  contributors 
to  the  "  American  Text -Book  of  Surgery,"  will  prove  of  exceptional  value  to 
the  advanced  student  who  has  adopted  that  work  as  his  text-book.  It  is  not 
only  the  syllabus  of  an  unrivalled  course  of  surgical  practice,  but  it  is  also  an 
epitome  or  supplement  to  the  larger  work. 

SYLLABUS  OF  OBSTETRICAL  LECTURES  in  the  Medical 
Department,  University  of  Pennsylvania.  By  RICHARD  C.  NORRIS, 
A.  M.,  M.  D.,  Demonstrator  of  Obstetrics  in  the  University  of  Pennsyl- 
vania. Third  edition,  thoroughly  revised  and  enlarged.  Crown  8vo. 
Price,  Cloth,  interleaved  for  notes,  $2.00  net. 

"  This  work  is  so  far  superior  to  others  on  the  same  subject  that  we  take  pleasure  in  call- 
ing attention  briefly  to  its  excellent  features.  It  covers  the  subject  thoroughly,  and  will 
prove  invaluable  both  to  the  student  and  the  practitioner.  The  author  has  introduced  a 
number  of  valuable  hints  which  would  only  occur  to  one  who  was  himself  an  experienced 
teacher  of  obstetrics.  The  subject-matter  is  clear,  forcible,  and  modern.  We  are  especially 
pleased  with  the  portion  devoted  to  the  practical  duties  of  the  accoucheur,  care  of  the  child, 
etc.  The  paragraphs  on  antiseptics  are  admirable;  there  is  no  doubtful  tone  in  the  direc- 
tions given.  No  details  are  regarded  as  unimportant;  no  minor  matters  omitted.  We  ven- 
ture to  say  that  even  the  old  practitioner  will  find  useful  hints  in  this  direction  which  he  can- 
not afford  to  despise." — Neiv  York  Medical  Record. 


I  8  IV.   B.    SA  UNDER  S> 


OUTLINES  OF  OBSTETRICS:  A  Syllabus  of  Lectures  Deliv- 
ered at  Long  Island  College  Hospital.  By  CHARLES  JEWETT,  A.  M., 
M.  D.,  Professor  of  Obstetrics  and  Pediatrics  in  the  College,  and  Obstetri- 
cian to  the  Hospital.  Edited  by  HAROLD  F.  JEWETT,  M.  D.  Post  8vo, 
264  pages.  Price,  $2.00. 

Tli is  book  treats  only  of  the  general  facts  and  principles  of  obstetrics  :  these 
are  stated  in  concise  terms  and  in  a  systematic  and  natural  order  of  sequence, 
theoretical  discussion  being  as  far  as  possible  avoided ;  the  subject  is  thus 
presented  in  a  form  most  easily  grasped  and  remembered  by  the  student. 
Special  attention  has  been  devoted  to  practical  questions  of  diagnosis  and 
treatment,  and  in  general  particular  prominence  is  given  to  facts  which  the  stu- 
dent most  needs  to  know.  The  condensed  form  of  statement  and  the  orderly 
arrangement  of  topics  adapt  it  to  the  wants  of  the  busy  practitioner  as  a  means 
of  refreshing  his  knowledge  of  the  subject  and  as  a  handy  manual  for  daily 
reference. 


NOTES  ON  THE  NEWER  REMEDIES:  their  Therapeutic  Ap- 
plications and  Modes  of  Administration.  By  DAVID  CERNA,  M.  D., 
PH.D.,  Demonstrator  of  and  Lecturer  on  Experimental  Therapeutics  in 
the  University  of  Pennsylvania.  Post-octavo,  175  pages.  Price,  $1.25. 

The  work  takes  up  in  alphabetical  order  all  the  newer  remedies,  giving  their 
physical  properties,  solubility,  therapeutic  applications,  administration,  and 
chemical  formula. 

It  thus  forms  a  very  valuable  addition  to  the  various  works  on  therapeutics 
now  in  existence. 

Chemists  are  so  multiplying  compounds,  that,  if  each  compound  is  to  be  thor- 
oughly studied,  investigations  must  be  carried  far  enough  to  determine  the  prac- 
tical importance  of  the  new  agents. 

"Especially  valuable  because  of  its  completeness,  its  accuracy,  its  systematic  consider- 
ation of  the  properties  and  therapy  of  many  remedies  of  which  doctors  generally  know  but 
little,  expressed  in  a  brief  yet  terse  manner." — Chicago  Clinical  Review. 

"  A  timely  and  needful  book  ....  which  physicians  who  avail  themselves  of  the  use  of 
the  newer  remedies  cannot  afford  to  do  without." — The  Sanitarian. 

LABORATORY  EXERCISES  IN  BOTANY.  By  EDSON  S.  BASTIN, 
M.  A.,  Professor  of  Materia  Medica  and  Botany  in  the  Philadelphia  Col- 
lege of  Pharmacy.  With  over  75  plates.  (In  preparation.) 

This  work  is  intended  for  the  beginner  and  the  advanced  student,  and  it  fully 
covers  the  structure  of  flowering  plants,  roots,  ordinary  stems,  rhizomes,  tubers, 
bulbs,  leaves,  flowers,  fruits,  and  seeds.  Particular  attention  is  given  to  the  gross 
and  microscopical  structure  of  plants,  and  to  those  used  in  medicine.  Illustra- 
tions have  freely  been  used  to  elucidate  the  text,  and  a  complete  index  to  facil- 
itate reference  has  been  added. 

The  folding  charts  which  supplement  the  subjects  will  be  found  useful  in 
connection  with  the  study  of  the  text. 


CATALOGUE    OF  MEDICAL    WORKS.  19 

SAUNDERS'  POCKET  MEDICAL  LEXICON  ;  or,  Dictionary  of 
Terms  and  Words  used  in  Medicine  and  Surgery.  By  JOHN  M. 
KEATING,  M.  D.,  editor  of  "  Cyclopaedia  of  Diseases  of  Children,"  etc. ; 
author  of  the  "  New  Pronouncing  Dictionary  of  Medicine;  and  HENRY 
HAMILTON,  author  of  "  A  New  Translation  of  Virgil's  ^Eneid  into  Eng- 
lish Verse  ;"  co-author  of  a  "  New  Pronouncing  Dictionary  of  Medicine." 
A  new  and  revised  edition.  32mo,  282  pages.  Prices:  Cloth,  75  cents; 
Leather  Tucks,  $1.00. 

This  new  and  comprehensive  work  of  reference  is  the  outcome  of  a  demand 
for  a  more  modern  handbook  of  its  class  than  those  at  present  on  the  market, 
which,  dating  as  they  do  from  1855  to  J884,  are  of  but  trifling  use  to  the  student 
by  their  not  containing  the  hundreds  of  new  words  now  used  in  current  litera- 
ture, especially  those  relating  to  Electricity  and  Bacteriology. 

"  Remarkably  accurate  in  terminology,  accentuation,  and  definition."— Journal  of  Amer- 
ican Medical  Association. 

"  Brief,  yet  complete  ....  it  contains  the  very  latest  nomenclature  in  even  the  newest 
departments  of  medicine." — New  York  Medical  Record. 


SAUNDERS'  POCKET  MEDICAL  FORMULARY.  By  WILLIAM 
M.  POWELL,  M.  D.,  Attending  Physician  to  the  Mercer  House  for  Invalid 
Women  at  Atlantic  City.  Containing  1750  Formulas,  selected  from  several 
hundred  of  the  best-known  authorities.  Forming  a  handsome  and  con- 
venient pocket  companion  of  nearly  300  printed  pages,  with  blank  leaves 
for  Additions ;  with  an  Appendix  containing  Posological  Table,  Formulae 
and  Doses  for  Hypodermatic  Medication,  Poisons  and  their  Antidotes, 
Diameters  of  the  Female  Pelvis  and  Foetal  Head,  Obstetrical  Table,  Diet 
List  for  Various  Diseases,  Materials  and  Drugs  used  in  Antiseptic  Surgery, 
Treatment  of  Asphyxia  from  Drowning,  Surgical  Remembrancer,  Tables 
of  Incompatibles,  Eruptive  Fevers,  Weights  and  Measures,  etc.  Third 
edition,  revised  and  greatly  enlarged.  Handsomely  bound  in  morocco, 
with  side  index,  wallet,  and  flap.  Price,  $1.75  net. 

A  concise,  clear,  and  correct  record  of  the  many  hundreds  of  famous  formulae 
which  are  found  scattered  through  the  works  of  the  most  eminent  physicians 
and ' sttrgeons  of  the  world.  The  work  is  helpful  to  the  student  and  practitioner 
alike,  as  through  it  they  become  acquainted  with  numerous  formulas  which  are 
not  found  in  text-books,  but  have  been  collected  from  among  the  rising  genera- 
tion of  the  profession,  college  professors,  and  hospital  physicians  and  surgeons. 

"This  little  book,  that  can  be  conveniently  carried  in  the  pocket,  contains  an  immense 
amount  of  material.  It  is  very  useful,  and  as  the  name  of  the  author  of  each  prescription  is 
given  is  unusually  reliable." — New  York  Medical  Record. 

"  Designed  to  be  of  immense  help  to  the  general  practitioner  in  the  exercise  of  his  daily 
calling." — Boston  Medical  and  Surgical  Journal. 


20  W.   B.   SAUNDERS^ 


HOW  TO  EXAMINE  FOR  LIFE  INSURANCE.  By  JOHN  M. 
KEATING,  M.  D.,  Fellow  of  the  College  of  Physicians  and  Surgeons  of 
Philadelphia;  Vice- President  of  the  American  Psediatric  Society;  Ex- 
President  of  the  Association  of  Life  Insurance  Medical  Directors.  Royal 
8vo,  211  pages,  with  two  large  phototype  illustrations,  and  a  plate  pre- 
pared by  Dr.  McClellan  from  special  dissections ;  also,  numerous  cuts  to 
elucidate  the  text.  Second  edition.  Price,  in  Cloth,  $2.00  net. 

PART  I.,  which  has  been  carefully  prepared  from  the  best  works  on  Physical 
Diagnosis,  is  a  short  and  succinct  account  of  the  methods  used  to  make 
examinations ;  a  description  of  the  normal  condition  and  of  the  earliest 
evidences  of  disease. 

PART  II.  contains  the  Instructions  of  twenty-four  Life  Insurance  Companies  to 
their  medical  examiners. 

"  This  is  by  far  the  most  useful  book  which  has  yet  appeared  on  insurance  examination,  a 
subject  of  growing  interest  and  importance.  Not  the  least  valuable  portion  of  the  volume  is 
Part  II.,  which  consists  of  instructions  issued  to  their  examining  physicians  by  twenty-four 
representative  companies  of  this  country.  As  the  proofs  of  these  instructions  were  corrected 
by  th«  directors  of  the  companies,  they  form  the  latest  instructions  obtainable.  If  for  these 
alone,  the  book  should  be  at  the  right  hand  of  every  physician  interested  in  this  special  branch 
of  medical  science." — The  Medical  News,  Philadelphia. 


MANUAL  OF  MATERIA  MEDICA  AND  THERAPEUTICS. 
By  A.  A.  STEVENS,  A.  M.,  M.  D.,  Instructor  of  Physical  Diagnosis  in  the 
University  of  Pennsylvania,  and  Demonstrator  of  Pathology  in  the  Woman's 
Medical  College  of  Philadelphia.  435  pages.  Price,  Cloth,  #2.25. 

This  wholly  new  volume,  which  is  based  on  the  1890  edition  of  the  Pharma- 
copeia, comprehends  the  following  sections  :  Physiological  Action  of  Drugs  ; 
Drugs  ;  Remedial  Measures  other  than  Drugs  ;  Applied  Therapeutics  ;  Incom- 
patibility in  Prescriptions;  Table  of  Doses;  Index  of  Drugs;  and  Index  of 
Diseases  ;  the  treatment  being  elucidated  by  more  than  two  hundred  formulae. 

"The  author  is  to  be  congratulated  upon  having  presented  the  medical  student  with  as 
accurate  a  manual  of  therapeutics  as  it  is  possible  to  prepare."—  Therapeutic  Gazette. 

"  Far  superior  to  most  of  its  class  ;  in  fact,  it  is  very  good.  Moreover,  the  book  is  reliable 
and  accurate."—  New  York  Medical  Journal  . 

"The  author  has  faithfully  presented  modern  therapeutics  in  a  comprehensive  work.  .  .  . 
and  it  will  be  found  a  reliable  guide."  —  University  Medical 


Will  be  of  immense  service  to  the  busy  practitioner."—  Medical  Reporter  (Calcutta). 

Reliable  and  timely."  —  North  American  Practitioner. 

Concise,  up  to  date,  and  withal  comprehensive."  —  Pacific  Medical  Journal  . 


SAUNDERS'  QUESTION  COMPENDS, 

Arranged  in  Question  and  Answer  Form, 

THE  LATEST,  CHEAPEST,  and  BEST  ILLUSTRATED 
SERIES  OF  COMPENLS  EVER  ISSUED, 


Now  the  Standard  Authorities  in  Medical  Literature 


Students  and  Practitioners  in  every  City  of  the  United 
States  and  Canada. 


THE   REASON    WHY. 

They  are  the  advance  guard  of  "  Student's  Helps  " — that  DO  HELP;  they  are 
the  leaders  in  their  special  line,  well  and  authoritatively  written  by  able  m?n, 
who,  as  teachers  in  the  large  colleges,  know  exactly  what  is  wanted  by  a  student 
preparing  for  his  examinations.  The  judgment  exercised  in  the  selection  of 
authors  is  fully  demonstrated  by  their  professional  elevation.  Chosen  from  the 
ranks  of  Demonstrators,  Quiz-masters,  and  Assistants,  most  of  them  have  be- 
come Professors  and  Lecturers  in  their  respective  colleges. 

Each  book  is  of  convenient  size  (5x7  inches),  containing  on  an  average  250 
pages,  profusely  illustrated,  and  elegantly  printed  in  clear,  readable  type,  on 
fine  paper. 

The  entire  series,  numbering  twenty- four  subjects,  has  been  kept  thoroughly 
revised  and  enlarged  when  necessary,  many  of  them  being  in  their  fourth  and 
fifth  editions. 

TO   SUM    UP. 

Although  there  are  numerous  other  Quizzes,  Manuals,  Aids,  etc.  in  the  mar- 
ket, none  of  them  approach  the  "  Blue  Series  of  Question  Compends;"  and 
the  claim  is  made  for  the  following  points  of  excellence : 

1.  Professional  distinction  and  reputation  of  authors. 

2.  Conciseness,  clearness,  and  soundness  of  treatment. 

3.  Size  of  type  and  quality  of  paper  and  binding. 

*#*  Any  of  these  Compends  will  be  mailed  on  receipt  of  price. 

21 


22  W.   B.   SAUNDERS' 


x.  ESSENTIALS  OF  PHYSIOLOGY.  By  H.  A.  HARE,  M.  D.,  Pro- 
fessor of  Therapeutics  and  Materia  Medica  in  the  Jefferson  Medical  Col- 
lege of  Philadelphia;  Physician  to  St.  Agnes'  Hospital  and  to  the  Medical 
Dispensary  of  the  Children's  Hospital ;  Laureate  of  the  Royal  Academy 
of  Medicine  in  Belgium,  of  the  Medical  Society  of  London,  etc.  Third 
edition,  revised  and  enlarged  by  the  addition  of  a  series  of  handsome 
plate  illustrations  taken  from  the  celebrated  "  Icones  Nervorum  Capitis  " 
of  Arnold.  Crown  8vo,  230  pages,  numerous  illustrations.  Price,  Cloth, 
$1.00  net;  interleaved  for  notes,  $1.25  net. 

"An  exceedingly  useful  little  compend.  The  author  has  done  his  work  thoroughly  and 
we'll.  The  plates  of  the  cranial  nerves  from  Arnold  are  superb." — Journal  of  American 
Medical  Association. 


2.  ESSENTIALS   OF    SURGERY,  containing  also  Venereal   Diseases, 

Surgical  Landmarks,  Minor  and  Operative  Surgery,  and  a  Complete  De- 
scription, together  with  full  Illustrations,  of  the  Handkerchief  and  Roller 
Bandages.  By  EDWARD  MARTIN,  A.M.,  M. D.,  Clinical  Professor  of 
Genito-Urinary  Diseases,  Instructor  in  Operative  Surgery,  and  Lecturer  on 
Minor  Surgery,  University  of  Pennsylvania ;  Surgeon  to  the  Howard  Hos- 
pital ;  Assistant  Surgeon  to  the  University  Hospital,  etc.  Fifth  edition. 
Crown  8vo,  334  pages,  profusely  illustrated.  Considerably  enlarged  by 
an  Appendix  containing  full  directions  and  prescriptions  for  the  prepara- 
tion of  the  various  materials  used  in  Antiseptic  Surgery ;  also  several 
hundred  recipes  covering  the  medical  treatment  of  surgical  affections. 
Price,  Cloth,  $1.00;  interleaved  for  notes,  $1.25. 

"  Written  to  assist  the  student,  it  will  be  of  undoubted  value  to  the  practitioner,  contain- 
ing as  it  does  the  essence  of  surgical  work." — Boston  Medical  and  Surgical  Journal. 

"  Cleverly  combines  all  the  merits  of  condensation,  while  avoiding  the  errors  of  super- 
ficiality and  inaccuracy." — University  Medical  Magazine. 

3.  ESSENTIALS    OF    ANATOMY,  including  the  Anatomy  of  the 

Viscera.  By  CHARLES  B.  NANCREDE,  M.  D.,  Professor  of  Surgery  and 
of  Clinical  Surgery  in  the  University  of  Michigan,  Ann  Arbor;  Cor- 
responding Member  of  the  Royal  Academy  of  Medicine,  Rome,  Italy ; 
late  Surgeon  to  the  Jefferson  Medical  College,  etc.  Fifth  edition.  Crown 
8vo,  380  pages,  180  illustrations.  Enlarged  by  an  Appendix  containing 
over  sixty  illustrations  of  the  Osteology  of  the  Human  Body.  The  whole 
based  upon  the  last  (eleventh)  edition  of  Gray's  Anatomy.  Price,  Cloth, 
$l.oo;  interleaved  for  notes,  $1.25. 

"Truly  such  a  book  as  no  student  can  afford  to  be  without." — American  Practitioner 
and  News. 

"The  questions  have  been  wisely  selected    and  the  answers  accurately  and  concisely 
given." — University  Medical  Magazine. 


CATALOGUE    OF  MEDICAL    WORKS.  2$ 


4.  ESSENTIALS  OF  MEDICAL  CHEMISTRY,  ORGANIC  AND 

INORGANIC,  containing  also  Questions  on  Medical  Physics,  Chemical 
Physiology,  Analytical  Processes,  Urinalysis,  and  Toxicology.  By  LAW- 
RENCE WOLFF,  M  D.,  Demonstrator  of  Chemistry,  Jefferson  Medical  Col- 
lege ;  Visiting  Physician  to  the  German  Hospital  of  Philadelphia ;  Member 
of  Philadelphia  College  of  Pharmacy,  etc.  Fourth  and  revised  edition, 
with  an  Appendix.  Crown  8vo,  212  pages.  Price,  Cloth,  $1.00;  inter- 
leaved for  notes,  $1.25. 

"  The  scope  of  this  work  is  certainly  equal  to  that  of  the  best  course  of  lectures  on  Med- 
ical Chemistry." — Pharmaceutical  Era. 

"  We  could  wish  that  more  books  like  this  would  be  written,  in  order  that  medical  students 
might  thus  early  become  interested  in  what  is  often  a  difficult  and  uninteresting  branch  of 
medical  study." — Medical  and  Surgical  Reporter. 

5.  ESSENTIALS    OF   OBSTETRICS.     By  W.   EASTERLY   ASHTON, 

M.  D.,  Professor  of  Gynecology  in  the  Medico-Chirurgical  College  of 
Philadelphia;  Obstetrician  to  the  Philadelphia  Hospital.  Third  edition, 
thoroughly  revised  and  enlarged.  Crown  8vo,  244  pages,  75  illustrations. 
Price,  Cloth,  $1.00  ;  interleaved  for  notes,  $1.25. 

"  An  excellent  little  volume  containing  correct  and  practical  knowledge.  An  admirable 
compend,  and  the  best  condensation  we  have  seen." — Southern  Practitioner. 

"Of  extreme  value  to  students,  and  an  excellent  little  book  to  freshen  up  the  memory  of 
the  practitioner." — Chicago  Medical  Times. 

6.  ESSENTIALS    OF    PATHOLOGY    AND    MORBID    ANAT- 

OMY. By  C.  E.  ARMAND  SEMPLE,  B.  A.,  M.  B.,  Cantab.  L.  S.  A., 
M.  R.  C.  P.  Lond.,  Physician  to  the  Northeastern  Hospital  for  Children, 
Hackney;  Professor  of  Vocal  and  Aural  Physiology  and  Examiner  in 
Acoustics  at  Trinity  College,  London,  etc.  Crown  8vo,  174  pages,  illus- 
trated. Sixth  thousand.  Price,  Cloth,  $1.00;  interleaved  for  notes,  $1.25. 

"  A  valuable  little  volume — truly  a  multum  in  parvo." — Cincinnati  Medical  News. 

"The  volume  is  very  comprehensive,  covering  the  entire  field  of  pathology." — St.  Joseph 
Medical  Herald. 

7.  ESSENTIALS    OF  MATERIA    MEDICA,    THERAPEUTICS, 

AND  PRESCRIPTION-WRITING.  By  HENRY  MORRIS,  M.  D., 
late  Demonstrator,  Jefferson  Medical  College ;  Fellow  of  the  College  of 
Physicians,  Philadelphia;  co-editor  Biddle's  Materia  Medica;  Visiting 
Physician  to  St.  Joseph's  Hospital,  etc.  Fourth  edition.  Crown  8vo,  250 
pages.  Price,  Cloth,  $1.00;  interleaved  for  notes,  $1.25. 

"One  of  the  best  compends  in  this  series.  Concise,  pithy,  and  clear,  well  suited  to  the 
purpose  for  which  it  is  prepared." — Medical  and  Surgical  Reporter. 

"  The  subjects  are  treated  in  such  a  unique  and  attractive  manner  that  they  cannot  fail  to 
impress  the  mind  and  instruct  in  a  lasting  manner." — Buffalo  Medical  and  Surgical  Journal. 


24  W.   B.   SAUNDERS^ 


8,  g.  ESSENTIALS  OF  PRACTICE  OF  MEDICINE.  By  HENRY 
MORRIS,  M.  D.,  author  of  "Essentials  of  Materia  Medica,"  etc.,  with  an 
Appendix  on  the  Clinical  and  Microscopical  Examination  of  Urine,  by 
LAWRENCE  WOLFF,  M.  D.,  author  of  "  Essentials  of  Medical  Chemistry," 
etc.  Colored  (Vogel)  urine  scale  and  numerous  fine  illustrations.  Third 
edition,  enlarged  by  some  three  hundred  essential  formulae,  selected  from 
the  writings  of  the  most  eminent  authorities  of  the  medical  profession, 
collected  and  arranged  by  WILLIAM  M.  POWELL,  M.  D.,  author  of 
"Essentials  of  Diseases  of  Children."  Crown  8vo,  460  pages.  Price, 
Cloth,  $2.00. 

"The  teaching  is  sound,  the  presentation  graphic,  matter  as  full  as  might  be  desired,  and 
the  style  attractive."—  American  Practitioner  and  News. 

"A  first-class  practice  of  medicine  boiled  down,  and  giving  the  real  essentials  in  as  few 
words  as  is  consistent  with  a  thorough  understanding  of  the  subject." — Medical  Brief. 

"  Especially  full,  and  an  excellent  illustration  of  what  the  best  of  the  compends  can  be 
made  to  be." — Gaillard 's  Medical  Journal. 


10.  ESSENTIALS  OF  GYNAECOLOGY.  By  EDWIN  B.  CRAGIN, 
M.  D.,  Attending  Gynaecologist,  Roosevelt  Hospital,  Out-Patients'  Depart- 
ment; Assistant  Surgeon,  New  York  Cancer  Hospital,  etc.  Fourth  edi- 
tion, revised.  Crown  8vo,  198  pages,  62  fine  illustrations.  Price,  Cloth, 
$l.oo;  interleaved  for  notes,  $1.25. 

"  This  is  a  most  excellent  addition  to  this  series  of  question  compends.  The  style  is  con- 
cise, and  at  the  same  time  the  sentences  are  well  rounded.  This  renders  the  book  far  more 
easy  to  read  than  most  compends,  and  adds  distinctly  to  its  value." — Medical  and  Surgical 
Reporter. 

"  Useful  not  only  to  the  student  who  is  barely  at  the  threshold  of  professional  life,  but  to 
the  busy  practitioner  as  well." — New  York  Medical  Journal. 


ii.  ESSENTIALS  OF  DISEASES  OF  THE  SKIN.  By  HENRY  W. 
STELWAGON,  M.  D.,  Clinical  Lecturer  on  Dermatology  in  the  Jefferson 
Medical  College,  Philadelphia;  Physician  to  the  Skin  Service  of  the 
Northern  Dispensary ;  Dermatologist  to  Philadelphia  Hospital ;  Physician 
to  Skin  Department  of  the  Howard  Hospital ;  Clinical  Professor  of  Der- 
matology in  the  Woman's  Medical  College,  Philadelphia,  etc.  Third  edi- 
tion. Crown  8vo,  270  pages,  86  illustrations,  many  of  which  are  original. 
Price,  Cloth,  $i  oo;  interleaved  for  notes,  $1.25  net. 

"  An  immense  amount  of  literature  has  been  gone  over  and  judiciously  condensed  by  the 
writer's  skill  and  experience." — New  York  Medical  Record. 

"  The  book  admirably  answers  the  purpose  for  which  it  is  written.     The  experience  of  the 
reviewer  has  taught  him  that  just  such  a  book  is  needed." — New  York  Medical  Journal. 


CATALOGUE    OF  MEDICAL    WORKS.  2$ 


12.  ESSENTIALS  OF  MINOR  SURGERY,  BANDAGING,  AND 
VENEREAL  DISEASES.  By  EDWARD  MARTIN,  A.M.,  M.  D., 
author  of  "  Essentials  of  Surgery,"  etc.  Second  edition.  Crown  8vo, 
thoroughly  revised  and  enlarged,  78  illustrations.  Price,  Cloth,  $1.00; 
interleaved  for  notes,  #1.25. 

"  Characterized  by  the  same  literary  excellence  that  has  distinguished  previous  numbers 
of  this  series  of  compends." — American  Practitioner  and  News. 

"The  best  condensation  of  the  subjects  of  which  it  treats   yet  placed  before  the  pro- 
fession."— Medical  News,  Philadelphia. 

"  A  capital  little  book.     The  illustrations  are  remarkably  clear  and  intelligible." — Aus- 
tralian Medical  Gazette. 

"  We  have  nothing  but  praise  for  the  subject-matter  of  this  book." — Bristol  Medico-Chi- 
rurgical  Journal. 


13.  ESSENTIALS  OF  LEGAL  MEDICINE,  TOXICOLOGY, 
AND  HYGIENE.  By  C.  E.  ARMAND  SEMPLE,  M.  D.,  author  of  "  Es- 
sentials of  Pathology  and  Morbid  Anatomy."  Crown  8vo,  212  pages, 
130  illustrations.  Price,  Cloth,  $1.00  ;  interleaved  for  notes,  $1.25. 

"  The  leading  points,  the  essentials  of  this  too  much  neglected  portion  of  medical  science, 
are  here  summed  up  systematically  and  clearly." — Southern  Practitioner. 

"  But  for  the  author's  judicious  condensation  of  facts,  the  information  it  contains  would  be 
sufficient  to  fill  an  ordinary  octavo  volume." — College  and  Clinical  Record. 


14.  ESSENTIALS  OF  REFRACTION  AND  DISEASES  OF 
THE  EYE.  By  EDWARD  JACKSON,  A.  M.,  M.  D.,  Professor  of  Dis- 
eases of  the  Eye  in  the  Philadelphia  Polyclinic  and  College  for  Graduates 
in  Medicine  ;  Member  of  the  American  Ophthalmological  Society ;  Fel- 
low of  the  College  of  Physicians  of  Philadelphia ;  Fellow  of  the  American 
Academy  of  Medicine,  etc. ;  and  ESSENTIALS  OF  DISEASES  OF 
THE  NOSE  AND  THROAT.  By  E.  BALDWIN  GLEASON,  S.  B., 
M.  D.,  Clinical  Professor  of  Otology,  Medico-Chirurgical  College,  Phila- 
delphia ;  Surgeon  in  charge  of  the  Nose,  Throat,  and  Ear  Department  of 
the  Northern  Dispensary  of  Philadelphia ;  formerly  Assistant  in  the  Nose 
and  Throat  Dispensary  of  the  Hospital  of  the  University  of  Pennsylvania, 
and  Assistant  in  the  Nose  and  Throat  Department  of  tlje  Union  Dispen- 
sary, etc.  Two  volumes  in  one.  Second  edition.  Crown  8vo,  294  pages, 
124  illustrations.  Price,  Cloth,  $1.00;  interleaved  for  notes,  $1.25. 

"A  valuable  book  to  the  beginner  in  these  branches,  to  the  student,  to  the  busy  prac- 
titioner, and  as  an  adjunct  to  more  thorough  reading.  The  authors  are  capable  men,  and  as 
successful  teachers,  know  what  a  student  most  needs." — New  York  Medical  Record. 

"  Very  valuable,  since  in  both  sections  is  given  about  all  that  a  candidate  for  examination 
is  required  to  know." — Medical  Times  and  Hospital  Gazette. 


26  W.   B.    SAUNDERS' 


15.  ESSENTIALS  OF  DISEASES  OF  CHILDREN.    By  WILLIAM 
M.  POWELL,  M.  D.,  Attending  Physician  to  the  Mercer  House  for  Invalid 
Women  at  Atlantic  City,  N.J. ;  late  Physician  to  the  Clinic  for  the  Dis- 
eases of  Children  in  the  Hospital  of  the  University  of  Pennsylvania  and 
St.  Clement's  Hospital;  Instructor  in  Physical  Diagnosis  in  the  Medical 
Department  of  the  University  of  Pennsylvania.     Crown  8vo,  216  pages. 
Price,  Cloth,  $1.00;  interleaved  for  notes,  #1.25. 

"  This  work  is  gotten  up  in  the  clear  and  attractive  style  that  characterizes  the  Saunders 
Series.  It  contains  in  appropriate  form  the  gist  of  all  the  best  works  in  the  department  to 
which  it  relates." — American  Practitioner  and  News. 

"  The  book  contains  a  series  of  important  questions  and  answers,  which  the  student  will 
find  of  great  utility  in  the  examination  of  children." — Annats  o/  Gynaecology. 

16.  ESSENTIALS    OF    EXAMINATION  OF  URINE.     By    LAW- 
RENCE  WOLFF,  M.  D.,  author  of  "  Essentials  of  Medical  Chemistry,"  etc. 
Colored   (Vogel)   urine  scale  and  numerous   illustrations.      Crown   8vo. 
Price,  Cloth,  75  cents. 

"  A  little  work  of  decided  value." — University  Medical  Magazine. 

"  A  good  manual  for  students,  well  written,  and  answers,  categorically,  many  questions 
beginners  are  sure  to  ask." — New  York  Medical  Record. 

"  The  questions  have  been  well  chosen,  and  the  answers  are  clear  and  brief.  The  book 
cannot  fail  to  be  useful  to  students." — Medical  and  Surgical  Reporter. 

17.  ESSENTIALS    OF    DIAGNOSIS.      By   SOLOMON   SOLIS-COHEN, 
M.  D.,  Professor  of  Clinical  Medicine  and  Applied  Therapeutics  in  the 
Philadelphia  Polyclinic,  and  AUGUSTUS  A.  ESHNER,  M.  D.,  Instructor  in 
Clinical  Medicine,  Jefferson  Medical  College,  Philadelphia.     Crown  8vo, 
382  pages,  55  illustrations,  some  of  which  are  colored,  and  a  frontispiece. 
Price,  $1.50  net. 

"  A  good  book  for  the  student,  properly  written  from  their  standpoint,  and  confines  itself 
well  to  its  text." — New  York  Medical  Record. 

"Concise  in  the  treatment  of  the  subject,  terse  in  expression  of  fact.  .  .  .  The  work  is 
reliable,  and  represents  the  accepted  views  of  clinicians  of  to-day." — American  Journal  of 
Medical  Sciences. 

"  The  subjects  are  explained  in  a  few  well-selected  words,  and  the  required  ground  has 
been  thoroughly  gone  over." — International  Medical  Magazine. 

18.  ESSENTIALS  OF  PRACTICE  OF  PHARMACY.     By  Lucius 
E.  SAYRE,  M.  D.,  Professor  of  Pharmacy  and  Materia  Medica  in  the  Uni- 
versity of  Kansas.     Second  edition,  revised  and  enlarged.     Crown  Svo, 
200  pages.     Price,  Cloth,  $1.00;  interleaved  for  notes,  $1.25. 

"Covers  a  great  deal  of  ground  in  small  compass.  The  matter  is  well  digested  and 
arranged.  The  research  questions  are  a  valuable  feature  of  the  book." — Albany  Medical 
Annals. 

"  The  best  quiz  on  Pharmacy  we  have  yet  examined." — National  Drug  Register. 

"  The  veteran  pharmacist  can  peruse  it  with  pleasure,  because  it  emphasizes  his  grasp 
upon  knowledge  already  gleaned." — Western  Drug  Record. 


CATALOGUE    OF  MEDICAL    WORKS.  2J 


20.  ESSENTIALS  OF  BACTERIOLOGY:  A  Concise  and  Syste- 
matic Introduction  to  the  Study  o^  Micro-organisms.     By  M.  V. 
BALL,  M.  D.,  Assistant  in  Microscopy,  Niagara  University,  Buffalo,  N.  Y. ; 
late  Resident  Physician,  German  Hospital,  Philadelphia,  etc.    Second  edi- 
tion, revised.     Crown  8vo,  200  pages,  81  illustrations,  some  in  colors,  and 
5  plates.     Price,  Cloth,  $i. oo;  interleaved  for  notes,  $1.25. 

"  The  amount  of  material  condensed  in  this  little  book  is  so  great,  and  so  accurate  are 
the  formulae  and  methods,  that  it  will  be  found  useful  as  a  laboratory  handbook." — Medical 
Newt. 

"  Bacteriology  is  the  keynote  of  future  medicine,  and  every  physician  who  expects  success 
must  familiarize  himself  with  a  knowledge  of  germ-life — the  agents  of  disease.  This  little 
book,  with  its  beautiful  illustrations,  will  give  the  students,  in  brief,  the  results  of  years  of 
study  and  research  unaided." — Pacific  Record  of  Medicine  and  Surgery. 

"Thoroughly  practical,  very  concise,  clear,  well-written,  and  sufficiently  illustrated.  .  .  . 
The  best  book  of  the  kind  in  the  English  language." — Medical  and  Surgical  Reporter. 

21.  ESSENTIALS  OF  NERVOUS  DISEASES  AND  INSANITY, 

their  Symptoms  and  Treatment.  By  JOHN  C.  SHAW,  M.  D.,  Clinical 
Professor  of  Diseases  of  the  Mind  and  Nervous  System,  Long  Island  Col- 
lege Hospital  Medical  School ;  Consulting  Neurologist  to  St.  Catherine's 
Hospital  and  to  the  Long  Island  College  Hospital ;  formerly  Medical  Super- 
intendent King's  County  Insane  Asylum.  Second  edition.  Crown  8vo,  186 
pages,  48  original  illustrations,  mostly  selected  from  the  Author's  private 
practice.  Price,  Cloth,  $1.00;  interleaved  for  notes,  $1.25. 

"Clearly  and  intelligently  written." — Boston  Medical  and  Stirgical  Journal. 

"  A  valuable  addition  to  this  series  of  compends,  and  one  that  cannot  fail  to  be  appreciated 
by  all  physicians  and  students." — Medical  Brief. 

"  Dr.  Shaw's  Primer  is  excellent.  The  engravings  are  well  executed  and  very  interest- 
ing."— Medical  Times  and  Register. 

"  Written  with  great  clearness,  devoid  of  verbosity,  it  encompasses  in  a  brief  space  a  vast 
amount  of  valuable  information." — Pacific  Medical  Record. 

22.  ESSENTIALS   OF   PHYSICS.      By  FRED  J.    BROCKWAY,   M.  D., 
Assistant  Demonstrator  of  Anatomy  in  the  College  of  Physicians  and  Sur- 
geons, New  York.    Second  edition.     Crown  8vo,  320  pages,  155  fine  illus- 
trations.    Price,  Cloth,  $1.00  net ;  interleaved  for  notes,  $1.25  net. 

"  The  publisher  has  again  shown  himself  as  fortunate  in  his  editor  as  he  ever  has  been  in 
the  attractive  style  and  make-up  of  his  compends." — American  Practitioner  and  News. 

"Contains  all  that  one  need  know  of  the  subject,  is  well  written,  and  is  copiously  illus- 
trated."— New  York  Medical  Record. 

"  The  author  has  dealt  with  the  subject  in  a  manner  that  will  make  the  theme  not  only 
comparatively  easy,  but  also  of  interest."— Medical  News,  Philadelphia. 

"  Deserving  of  close  investigation  at  the  hands  of  students  and  physicians."—  American 
Gynecological  Journal. 


28  W.    B.   SAUNDERS'    CATALOGUE. 


23.    ESSENTIALS    OF    MEDICAL    ELECTRICITY.     By   D.    D. 

STEWART,  M.  D.,  Demonstrator  of  Diseases  of  the  Nervous  System  and 
Chief  of  the  Neurological  Clinic  in  the  Jefferson  Medical  College ;  Phy- 
sician to  St.  Mary's  Hospital  and  to  St.  Christopher's  Hospital  for  Chil- 
dren, etc. ;  and  E.  S.  LAWRANCE,  M.  D.,  Chief  of  the  Electrical  Clinic, 
and  Assistant  Demonstrator  of  Diseases  of  the  Nervous  System  in  the 
Jefferson  Medical  College,  etc.  Crown  8vo,  148  pages,  65  illustrations. 
Price,  Cloth,  $1.00;  interleaved  for  notes,  $1.25. 

"Clearly  written,  and  affords  a  safe  guide  to  the  beginner  in  this  subject." — Boston  Med- 
ical and  Surgical  Journal. 

"  The  subject  is  presented  in  a  lucid  and  pleasing  manner." — New  York  Medical  Record. 

"  A  little  work  on  an  important  subject,  which  will  prove  of  great  value  to  medical  students 
and  trained  nurses  who  wish  to  study  the  scientific  as  well  as  the  practical  points  of  elec- 
tricity."—  The  Hospital,  London. 

"  The  selection  and  arrangement  of  material  are  done  in  a  skilful  manner.  It  gives,  in  a 
condensed  form,  the  principles  and  science  of  electricity  and  their  application  in  the  practice 
of  medicine." — Annals  of  Surgery. 

"  The  compilation  is  a  good  one,  and  will  be  found  useful  both  to  students  and  to  men  in 
practice." — New  Zealand  Medical  Journal . 


24.    ESSENTIALS    OF    DISEASES    OF    THE    EAR.     By  E.  B. 

GLEASON,  S.  B.,  M.  D.,  Clinical  Professor  of  Otology,  Medico- Chirurgical 
College,  Philadelphia;  Surgeon  in  Charge  of  the  Nose,  Throat,  and  Ear 
Department  of  the  Northern  Dispensary  of  Philadelphia;  formerly  As- 
sistant in  the  Nose  and  Throat  Dispensary  of  the  Hospital  of  the  Univer- 
sity of  Pennsylvania,  and  Assistant  in  the  Nose  and  Throat  Department 
of  the  Union  Dispensary.  89  illustrations.  Price,  Cloth,  $1.00 ;  inter- 
leaved for  notes,  $1.25. 

This  latest  addition  to  the  Saunders  Compend  Series  accurately  represents 
the  modern  aspect  of  otological  science.  The  effort  has  been  made  to  state  the 
Essentials  of  Otology  concisely,  without  sacrificing  accuracy  to  brevity,  and  the 
book,  while  small  in  compass,  is  logically  and  capably  written;  it  comprises  up- 
ward of  150  pages,  with  89  illustrations,  most  of  which  are  from  original 


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